Can I run a 1500 Watt inverter off a 100ah agm deep cycle battery while the vehicle is running?

[Solar_Lex]

Goal
Live out of our campervan for 5-6 months. We just bought a 2001 Sprinter campervan in New Zealand. We fly into NZ in November from Canada.


Currently Campercan System:
- 100ah agm battery
- 500w modified wave inverter
- 90A Voltage-sensitive relay module (13.7 cut in, 12.8v cut out)
- 2 panels of unknown watts (the past owner said when the van sat for many days not driving the battery tops up each day with the fridge running)
- Mppt charge controller of unknown size
- I plan to replace the alternator to a 150A, maybe 200A. (Vin says it’s 90A stock)


Why a 1500-watt inverter
I read I should change the inverter since a modified sine wave inverter could damage our MacBook work laptops. So if I have to upgrade it anyways I was hoping to get at a 1500-watt inverter. Since 1500w (3000 Peak) can run most household electronics. I also would like the ability to run a blender for about 30 seconds a day lol. 60 max. 60 seconds doesn't seem long until you run a blender for that long lol.


My plan to run 1500 watt inverter. Do you think it’ll work?
I’m guessing 1500w would really damage a 100ah agm house battery; So my plan is to run it off the house battery, starter battery, and alternator. This way the power will be divided among the 3 sources of power. A blender doesn’t run for long so I’ll be able to top off the starter battery before shutting off the vehicle. Were talking about starting the van for about 1-2 mins, once a day. The alternator will be at least a 150A which is 60amps bigger than stock. I know you don’t get the full amps at idle but I think it should still give a fair amount of power.


My electrical wire plan
My electrical plan is fairly simple. Change the wire that goes from the starter battery to the house battery to instestead run from the starter battery to the inverter positive post. Than run another wire from the house batter to the positive post of the inverter. This way the inverter will pull power from both wires coming from different sources. The wire that goes to the inverter to the starter battery will have a smart isolator switch with a manual override button. If I want to use the blender I’ll just have to push the manual override button to connect everything together.


Plan to stop inverter pulling 1500w when vehicle is off
I know breakers/fuses normally protect the wire, but in this case I could size the breaker going from the inverter to the house battery to limit the power that is pulled from the house battery. I’m thinking maybe a 50amp breaker??? idk, idk because I don’t know what a normal pull people accept from AGM batteries.

Where I’m stuck
I don’t have enough experience to guess if this system will work because:
- I don’t know what is a normally acceptable constant power draw from an AGM battery to find a good fuse size from the house battery to the inverter.
- I don’t know how to even guess the amount an alternator will provide to the Pure sine wave inverter with the other two batteries connected.


My Canadian campervan test may help someone answer my questions
With my canadian campervan I did Is I disconnected my Lithium house batteries and connected the house system to my starter battery. Then I ran my big household Vitamix blender off the van’s 3000w inverter. I have a dedicated battery monitor on my starter battery and watched to see how many watts it pulled with the vehicle running. It was draining 450 watts from the battery at start and slowly pulling less and less. I reconnected the house lithium batteries and ran the blender to check how many watts the blender was pulling in total. The blender was pulling 1.3kw so around 1350watts.
This test made me think the 1500watt inverter might work for a blender in my NZ campervan because even though it has a 150amp alternator it would have the house battery also providing power to the inverter, Unlike my Canadian campervan test.
I have almost the same van in Canada. They’re both model sprinters but my Canadian one is slightly newer with a bigger motor. 2.7L vs 2.1L. I don’t think the motors should matter since the idle speed is the same and the alternators are interchangeable. Also, my Canadian one is running a 200A alternator.


Sidenote: I’m not keeping the New Zealand Campervan
After our 5-6 months in New Zealand I plan to sell the campervan. So I don’t want to invest too much money in the power system. I also don’t want to spend too much time working on the power system and not experience the beauty of NZ. I think it will be the last time in my life that I go there so I want to experience the country. I also want to leave a Safe good system for the next owner of the vehicle. I’m happy with the upgrade cost of a 1500 pure inverter some breakers and possibly some bigger wires. The alternator needs to be changed regardless. It’s never been changed and the pulley is seized.


Any advice would be awesome.

 

[Whats_per_question]

Hi Solar_Lex,
A great big preemptive welcome to NZ!
You said ... "guessing 1500w would really damage a 100ah agm house battery".
A 1500w inverter drawing full surge load (3000w) will pull ~250A, so unless your AGM has that kind of CCA (if its actually a starter battery) or a BMS that can do that (unlikely), then you will cook that battery IMO.
I would consider how much 12v gear you have, and if you are not fully invested in 12v, then go with 24v or even 48v, with a victron DCDC to charge from alternator when driving.
That way your currently will be halved (or quartered with 48v) and cable size can be much smaller.
If you are coming into NZ via Auckland, then i can give you a really good contact in Tauranga (not too far away) who does a lot of vans.
If you are coming near Taranaki let me know, i'll tell you some good places to visit that you might otherwise not hear about.

 

[Solar Guppy]

Just an FYI, most electronic equipment rectifies the AC to DC anyways and using a "modified" sine wave aka square wave inverter will be fine with computers or electronic accessories

 

[Solar_Lex]

Just an FYI, most electronic equipment rectifies the AC to DC anyways and using a "modified" sine wave aka square wave inverter will be fine with computers or electronic accessories

Thanks for the Reply Guppy

Hmmm I'm a bit confused:

I just did some deeper research on the matter and it seems that people have indeed been running off modified sine wave inverters with no apparent issues. That being said there seems to be at least a couple of people on each forum saying don't do it, or they wouldn't do it. Most of those people don't have a detailed explanation as to why. Most say "laptops are sensitive."

The best explanation I found was from this forum. There was talk that a modified wave inverter won't hurt the laptop but significantly reduce the battery life of the laptops. Also in the thread, there was someone saying that MacBooks are more sensitive than other laptops and he has a worker that destroyed his MacBook on a modified sine wave inverter. I think I read something about pulsing dc waves or something. Perhaps the person's who's MacBook got damage was running it with a battery that completely died and it was taking the full brunt of the inverters dc power??? :s idk.

Any thoughts on my idea of running the 1500 with the engine started?

 

[Solar_Lex]

Hi Solar_Lex,
A great big preemptive welcome to NZ!
You said ... "guessing 1500w would really damage a 100ah agm house battery".
A 1500w inverter drawing full surge load (3000w) will pull ~250A, so unless your AGM has that kind of CCA (if its actually a starter battery) or a BMS that can do that (unlikely), then you will cook that battery IMO.
I would consider how much 12v gear you have, and if you are not fully invested in 12v, then go with 24v or even 48v, with a victron DCDC to charge from alternator when driving.
That way your currently will be halved (or quartered with 48v) and cable size can be much smaller.
If you are coming into NZ via Auckland, then i can give you a really good contact in Tauranga (not too far away) who does a lot of vans.
If you are coming near Taranaki let me know, i'll tell you some good places to visit that you might otherwise not hear about.

Hmm I see my link and format didn't copy over when I copy and pasted my thread from google docs. I just added the battery link and bold formatting back for easier reading.

Thanks for the big warm welcome to NZ. I may take you up on the offer of what is to do around that area if I come by. As for making the system, I'm not bad at that. I have done 3 campervan systems already but when I designed it I always left lots of room in all areas. This is a system I didn't design that I'm modifying to do what I need for the few months I have it.

The main question I'm asking is not if I can run 1500 watts off a house battery, but if I can run 1500 watts off a house battery, starter battery, and alternator.
Also what is the amount of amps that people feel comfortable pulling from their 100 AGM deep cycle battery? What are the max amps people would be comfortable pulling from their battery for about 1 min? Any rule of thumbs?

 

[Texas-Mark]

then you will cook that battery IMO.

Not going to "cook" the AGM battery.

 

[Texas-Mark]

Just an FYI, most electronic equipment rectifies the AC to DC anyways and using a "modified" sine wave aka square wave inverter will be fine with computers or electronic accessories

Not necessarily. Some electronics specifically advise against it, depending on how the power supply (adapter) is designed. All will get hotter than with a pure sine wave. With prices these days, I see no reason to ever go modified sine wave.

 

[Solar_Lex]

I'm planning to get the pure sine wave inverter regardless. The work macbooks are too expensive and important to risk any damage. Not just the price of the MacBooks but the money lost with not having one. I don't have that much free income hints the 2001 sprinter lol.

 

[pollenface]

Hi @Solar_Lex

I ran a 2000w pure sine wave inverter (with built in soft start) directly from my vehicles alternator for many years. Thus, appliances were only used while the engine was idling. I only had a 70a alternator. Cranking batteries also have high surge capacity which may assist in starting loads (like big fat winches).

I ran a 600w blender on a regular basis with engine idling (banana milk shakes). Occasionally ran a 750w angle grinder.

 

[Whats_per_question]

Not going to "cook" the AGM battery.

Texas-Mark - His battery specs (according to the link) say

Battery Peak Current

1A

Presuming that *has* to be wrong, i'm guessing it actually means 1C (ie 100A). The spec also says the 1hr capacity is 63Ah

1 Hour Capacity

63Ah

To get 63Ah out of that battery in 1h means drawing 63A, so lets say the correct peak current is at least 63A.

When you say he isn't going to cook an AGM battery, are you basing that on him only drawing 1.3kw (the blender, which will pull around 108A) for short periods?
Do you have any refs that show drawing >1C on AGM is fine?
I've always treated AGM as having a charge limit of 0.2C, discharge of 0.5C

 

[Texas-Mark]

When you say he isn't going to cook an AGM battery, are you basing that on him only drawing 1.3kw (the blender, which will pull around 108A) for short periods?

Yes. And I generally use the term "cook" for an overcharged battery, not trying to draw more than it can supply.

Do you have any refs that show drawing >1C on AGM is fine?

Only that I have done it (short term) many times with no noticeable ill effects

 

[Solar_Lex]

Hi @Solar_Lex

I ran a 2000w pure sine wave inverter (with built in soft start) directly from my vehicles alternator for many years. Thus, appliances were only used while the engine was idling. I only had a 70a alternator. Cranking batteries also have high surge capacity which may assist in starting loads (like big fat winches).

I ran a 600w blender on a regular basis with engine idling (banana milk shakes). Occasionally ran a 750w angle grinder.

Awesome info thank you.

What's a "soft start"?

 

[Solar_Lex]

Texas-Mark - His battery specs (according to the link) say

Battery Peak Current

1A

Presuming that *has* to be wrong, i'm guessing it actually means 1C (ie 100A). The spec also says the 1hr capacity is 63Ah

1 Hour Capacity

63Ah

To get 63Ah out of that battery in 1h means drawing 63A, so lets say the correct peak current is at least 63A.

When you say he isn't going to cook an AGM battery, are you basing that on him only drawing 1.3kw (the blender, which will pull around 108A) for short periods?
Do you have any refs that show drawing >1C on AGM is fine?
I've always treated AGM as having a charge limit of 0.2C, discharge of 0.5C

Thanks for your post.


I think you helped me understand the C rating now. Thank you
If I combine what your saying with the battery specs page it seems the slower... or smaller the amps you pull from the battery, the more amps the battery will give you before it dies. So it seems the battery becomes more and more inefficient with bigger and bigger draws.


1C @ 63ah = 750 inverter?
So would most people with a battery that has a 1C@63 be happy using a 750W inverter? Would they fuse the positive wire going to the inverter with a 65 or 60-amp fuse? (63amps draw = 756 watts draw) ( (Assuming of course that the wire is big enough for fuse rating.)


Would a 60/65 amp fuse protect a 1c@63ah battery using a 1500-watt fuse?
If a 60 or 65-amp fuse would protect the battery then I think this should work going by my Canadian Campervan test I posted in post one.


My math says 625 Max draw to run the 1500watt with House & starter batter + 150 Alternator. (Please correct me if I'm thinking Wrong)
- 450 watts current battery load on my identical Canadian campervan with a 200 amp alternator.
- 600 watts would be the conservative extra load added to the NZ van system using a 150 alternator (50x12=600 watts)
- 200 watts is the conservative amount added if using a 1500-watt device and not the 1.3+kw (1300w) load I used for the Canadian test.
- Total of 1250 watts is a conservative battery load for my NZ van using a 1500-watt device while the engine is running (450+600+200)
- 625 watts is the 1250 battery divided among the two batteries (1250/2).
* This would also give 125 watts free in case the house battery provides more for some reason (I'm not an expert)


Thoughts anyone

 

[JoeHam]

Goal




Plan to stop inverter pulling 1500w when vehicle is off
I know breakers/fuses normally protect the wire, but in this case I could size the breaker going from the inverter to the house battery to limit the power that is pulled from the house battery. I’m thinking maybe a 50amp breaker???

Obviously this would limit you to around 700W loads considering inverter inefficiency so perhaps after choosing an inverter this can be revisited.

Edit: we posted at the same time.

When you choose an inverter the math is a bit simpler. For your most recent post let’s assume you end up with an inverter that is 85% efficient. In that case divide all your current numbers by 0.85 to get the correct current load.

Since we are talking about breakers I would encourage you to use Amperage as your common unit instead of mixing Watts in there.

For LiFePO4 batteries 12.8V nominal is used but obviously you will want to allow for more current as you drain your battery to a lower Voltage.

 

[littleharbor2]

Do you really need a 1500 watt inverter? Maybe try your largest load on your smaller inverter. Idle draw goes up with larger inverters. Also the inverter's efficiency is usually worse with lower loads. I ran my camper with a 750 watt inverter and about the only load that gave me problems was trying to run some power tools which obviously aren't typical loads when camping,otoh, the blender always was being used.

 

[JoeHam]

A completely different way to approach your problem would be to keep whatever small inverter you have now as it is for small loads.

A larger inverter for heavy loads could be added, with ignition sensing (a trivial matter) so that the heavy load inverter only comes on while the engine is running. Many inverters have such a relay built in.

This avoids the inherent issues of trying to use breakers for a purpose they really were not intended for.

As an added benefit you would have a lower idle consumption if just the small inverter was left connected when the engine was off.

 

[Solar_Lex]

Do you really need a 1500 watt inverter? Maybe try your largest load on your smaller inverter. Idle draw goes up with larger inverters. Also the inverter's efficiency is usually worse with lower loads. I ran my camper with a 750 watt inverter and about the only load that gave me problems was trying to run some power tools which obviously aren't typical loads when camping,otoh, the blender always was being used.

What fuse size did you use on the 750-watt inverter?


Ummm, idk what size inverter I would need?
All I know is I'm living out of the van for 5-6 months in a country far from anyone I know. No friends or house for me to go do things at. That being said it has already been lived in by a couple for months that was in the same boat. I was using blenders as an item to determine how big I would need since I would like to use a blender and it uses an above-average amount of power lol.

Need new inverter regardless because nots pure wave
- I have done a fairly deep research and it seems the modified inverters can damage Macbooks or in the least significantly decrease the battery life. Campervan currently has a modified inverter. I may of misunderstand what people were talking about but it seems there is a slight pulsing of the dc power when using a modified inverter that causes devices to run hotter which hurts laptop batteries and could destroy electronics that can't take the extra heat. Macbook seem to be more sensitive than other laptops. My and my wife have two expensive work laptops that we need to work on during our whole trip.

 

[Solar_Lex]

A completely different way to approach your problem would be to keep whatever small inverter you have now as it is for small loads.

A larger inverter for heavy loads could be added, with ignition sensing (a trivial matter) so that the heavy load inverter only comes on while the engine is running. Many inverters have such a relay built in.

This avoids the inherent issues of trying to use breakers for a purpose they really were not intended for.

As an added benefit you would have a lower idle consumption if just the small inverter was left connected when the engine was off.

I love the outside-the-box thinking. The problem is I don't trust the currently modified sine wave inverter to run our two expensive work Macbooks.

I am thinking of using an ignition-triggered relay for the second wire to the inverter, the wire from the starter battery that is. Instead of using one big breaker, I would use two breakers half size breakers, that combined would give the full load to the inverter. This would avoid the inverter from accidentally pulling to much from the house battery when the vehicle is off, It would just pop the half-size breaker.

 

[littleharbor2]

This was a long time ago. It was a cheap modified type inverter. To be honest, I didn't have it fused. The only item I used that didn't like he inverter was a orbital sander with electronic speed control. It refused to run. Everything else ran fine.That being said, I would have gone pure sine wave if I could have afforded it. I built this camper from scratch.

 

[Solar_Lex]

Do you really need a 1500 watt inverter? Maybe try your largest load on your smaller inverter. Idle draw goes up with larger inverters. Also the inverter's efficiency is usually worse with lower loads. I ran my camper with a 750 watt inverter and about the only load that gave me problems was trying to run some power tools which obviously aren't typical loads when camping,otoh, the blender always was being used.

why 1500 watt
- simply because that is what the internet is saying would run most blenders. idk

Inverter size options
- 600, 800, 1000, 1500 is what my seller is offering.
- I have bought 2 inverters for my other campervans from this Alibaba seller that I really liked. It took me a lot of time to choose that seller/inverters the first 2 times, so I was wanting to buy from him again. He also ships to NZ for free.