Amperetime / CHINS 12V 100AH enough to start RV Generator?

eXodus

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Hello,

my 2x 12V deepcycle batteries in my RV are just about to die. I got a 5500w Onan generator, which starts from those batteries.


The Amperetime and CHINS 100AH have those ratings:
Maximum Continuous Charging Current: 100A

Maximum Continuous Discharging Current: 100A

Maximum Permanent Discharging Current: 280A 5Sec.


My cheap clamp on amp meter doesn't give me a good amp reading when the generator starts, Shows like 3 amps, lol.
It starts pretty quickly.

Anyone tried to start a generator with a LFP battery? Amperetime / CHINS 12V 100AH ?

What can happen worst case? BMS shuts the battery down?
 

JeepDaddy

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I just tested my Onan 5500 Emerald Gold generator yesterday and the starter pulled about 75-80 amps according to my Victron Smartshunt. My JBD 150A BMS on my 280AH cells had no problems.

I'm not sure what type of RV you have, but for FWIW, my hydraulic leveling system pulls 90 amps.
 

eXodus

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I just tested my Onan 5500 Emerald Gold generator yesterday and the starter pulled about 75-80 amps according to my Victron Smartshunt. My JBD 150A BMS on my 280AH cells had no problems.

I'm not sure what type of RV you have, but for FWIW, my hydraulic leveling system pulls 90 amps.
Thanks,

I got the same Onan 5500 Emerald from around 2003. That gives me a good baseline 75-80 Amp

I got a RVision (Monaco) 24FT Class A, I don't have a Leveling system yet. But when I get one then I would get the electric version.
 

Lt.Dan

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I read the manual on my Onan 5500, and it specifically recommends a battery with no less than 350 Cranking Amps.

Then again, my 1 BattleBorn battery started it faster than 1x SLA.
 

eXodus

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I read the manual on my Onan 5500, and it specifically recommends a battery with no less than 350 Cranking Amps.

Then again, my 1 BattleBorn battery started it faster than 1x SLA.
Battleborn specs:

"Our BMS keeps you and your battery safe and ensures your battery will last for many years.
• 100 Amps Continuous
• 200 Amps Surge for 30 Seconds
• ½ Second Surge for Loads Over 200 Amps"

somewhat similar to the Amperetime / Chins, they state 280A for 5 seconds - my generator doesn't usually need 5 seconds to crank up.
But it got 2x 650CCA batteries connected so has access to 1300A

Hm. It shouldn't damage the LFP? I start it about once every other week and many times I run the generator is actually while driving the RV - when the Alternator is helping :p

Worst case I just get a second 100AH batteries. I want to use the drop ins vs. DIY because they are IP65 since they will be living behind my front bumper. So will get occasional water, and I'm not trusting myself enough to built something waterproof :p
 

jharrell

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Pretty hard to capture the initial inrush with a normal amp meter since its so fast, you need a high sample rate meter, they make special ones for that purpose. When they list say 350 cranking amps thats the initial inrush spike, which then settles into the 75-80 amps while cranking that you see on a shunt meter.

This is what it looks like on a scope, all of the large spike is under 1/2 second:

IMG_1491.jpg

I am planning on doing 2 100ah LFP batteries on my RV soon which has an Onan 4000 and everything I can find shows no one having any issues with them starting generators, I see 70-80 amps on my Magnums shunt while its cranking and needs 350 CCA according to specs.
 

eXodus

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Pretty hard to capture the initial inrush with a normal amp meter since its so fast, you need a high sample rate meter, they make special ones for that purpose. When they list say 350 cranking amps thats the initial inrush spike, which then settles into the 75-80 amps while cranking that you see on a shunt meter.

This is what it looks like on a scope, all of the large spike is under 1/2 second:

View attachment 60216

I am planning on doing 2 100ah LFP batteries on my RV soon which has an Onan 4000 and everything I can find shows no one having any issues with them starting generators, I see 70-80 amps on my Magnums shunt while its cranking and needs 350 CCA according to specs.

That's a good chart, thanks!
The question is, will a single 100ah LFP shut down *bms / or get damaged when doing that?

I've read something about Cell damage when you pull to high camps.

Seems like your plan with 2x 100AH LFP should be more then enough, since the specs would turn out to 200A continues - which the stroking of the engine requires.

While one battery only does that for 5 seconds (cold day might be a tight fit)
 

eXodus

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Found a interesting discussion about that topic in iRV2


So basically saying - that due to almost no voltage drop in a LFP battery - the cranking amps are lower - A lead battery cranks a 10-7V while the LFP is at stuck at 12-13V even larger generators in this thread are mentioned (10kw Diesel) are only pulling 70A (no idea how that was measured)

But it makes sense P = V * I

Power is voltage times current. The starter needs a certain power, the CCA definition is for LEAD. there the voltage drops while cranking.
Onan puts up 350 CCA - that might be at 7-10V

For inrush 7V* 350A = 2450W up to 10V * 350A = 3500W

For cranking (from chart) 7V* 120A = 840W up to 10V * 120A = 1200W

Going from lithium for best case = 840W / 13V = 64A (close to what is observed in this on the other forum)
LFP worst case 1200W / 12V = 100A

Any objections in my math?
 

jharrell

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Based on what I know its really whether the BMS decides to shut down or not and most BMS's do not react fast enough so they have a small window of say 1/2 second unlimited current.

I haven't heard of LFP batteries getting damaged by a very short inrush like that, its definitely not good sustained but like most electrical device that can take very short bursts far exceeding their rated specs, same with the BMS.

Here is a thread showing no issues starting a Onan 4000 off first two 120a BMS, then later in the thread just one:

https://diysolarforum.com/threads/starting-my-onan-4k-with-my-lifepo.15367/

Yes the LFP battery has less voltage sag under load and therefore amps will be lower, its is a much stiffer voltage source
 

MPRanger

Beefield, GA 30461
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Beefield Georgia
Hello,

my 2x 12V deepcycle batteries in my RV are just about to die. I got a 5500w Onan generator, which starts from those batteries.


The Amperetime and CHINS 100AH have those ratings:
Maximum Continuous Charging Current: 100A

Maximum Continuous Discharging Current: 100A

Maximum Permanent Discharging Current: 280A 5Sec.


My cheap clamp on amp meter doesn't give me a good amp reading when the generator starts, Shows like 3 amps, lol.
It starts pretty quickly.

Anyone tried to start a generator with a LFP battery? Amperetime / CHINS 12V 100AH ?

What can happen worst case? BMS shuts the battery down?
Small generators generally don’t require a great deal of starting amps, however LiFePO4, they are not designed to start motors. Yes, your BMS should clamp excess in ms’s if programmed to do so. Why are you choosing to use a deep cycle LiFePO4 battery? Is it because they have reached ‘end of life’? These are designed to produce AC power with an inverter and be charged via PV. Are you asking if this will further shorten their life?
 

jharrell

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Small generators generally don’t require a great deal of starting amps, however they are not designed to start motors. Yes, your BMS should clamp excess in ms’s if programmed to do so. Why are you choosing to use a deep cycle LiFePO4 battery? These are designed to produce AC power with an inverter and be charged via PV.
Most RVs are wired to start the generator from the house batteries, it can be significant work to rewire to starting battery, not sure why its does this way. I have thought about rewiring mine but it would involve some significant work for I am not sure much benefit.

Do you know how many ms your typical BMS will clamp on excess amperage? Battleborn seems to say 500ms of no clamping then 30 seconds at 200 amps.

Why do you say these batteries are not designed to start motors? They seem to be designed to put out a certain constant amperage (1C) with the ability to handle short periods of higher amperage draw regardless of the load attached. Is there a different cell design that is or is it just the BMS programming? I can't seem to find much info on this. In lead acid its based on the plate thickness for deep cycle vs starting whereas this doesn't seem to apply to LFP.
 
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eXodus

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Small generators generally don’t require a great deal of starting amps, however LiFePO4, they are not designed to start motors. Yes, your BMS should clamp excess in ms’s if programmed to do so. Why are you choosing to use a deep cycle LiFePO4 battery? Is it because they have reached ‘end of life’? These are designed to produce AC power with an inverter and be charged via PV. Are you asking if this will further shorten their life?
A pair of deep cycle AGM these days runs $400 and will hold up 3-5 years.

Buying one 100AH LFP batteries is $500

I get about 60 days of annual of use in my camper - So the 4000 advertised cycles should last till the camper falls apart :p The LFP will age out before I get those cycles.

I'm don't use the generator much, best guess - 20-30 times a year. So it's not something the batteries have to endure every day.
Half of those starts are also supported by the alternator of the main engine - since on very hot travel days I run the generator to run overhead A/C unit.

My plan is now to go ahead and buy 1x 100AH and see how it does with Generator. If it's doing weird stuff I get a second one.
I just don't want to spend a ton of money now since the RV is getting a 24/V48V system with many kwh (5-10) of battery capacity next winter.

And I already researched - a buck converter can not start a generator. So I need the to keep the 12V system around.
 

eXodus

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Most RVs are wired to start the generator from the house batteries, it can be significant work to rewire to starting battery, not sure why its does this way. I have thought about rewiring mine but it would involve some significant work for I am not sure much benefit.

Yes changing the 12V system for the generator is next to impossible with tearing apart the engine bay.

Further you loose a measure of redundancy. if you are wiring the generator to the engine battery, Self driving RVs have nice double redundancy built in.

When you run down your house batteries:
- Start the main engine - it charges the house batteries so you can get the generator started.

When the engine battery drains:
- Start the generator - it charges the house batteries and you can use momentary connect switch start the main engine

When you put Solar in the mix - you have a 3rd layer of redundancy. 3 different power sources.
Since I'm wild camping in the middle of nowhere with no reception (on purpose) those are very valuable points to me.
 

jharrell

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Yes its true about starting redundancy, if my house batteries are dead I could start my main engine and then the ACR would connect and charge the house enough to start the genny and vis versa. I also have 300w solar and my jeep toad for jumping and a little lithium jump starter in the jeep, so plenty redundancy :).

My two Lifeline AGM's are going on 6 years old and starting to show signs of wear and I would really like to move to LFP now that prices are almost the same and there would be many benefits to 200ah LFP vs 200ah of even really good AGM's like the Lifelines, so I am starting to plan which batteries to get and have been trying to confirm the generator starting won't be an issue.

As an interesting note my Lifelines are "deep cycle" are also rated for starting and can even charge at 5C safely! So even in the lead acid world deep cycle doesn't away mean they can't be used for engine starting. Even with flooded deep cycle most rv start the generator off the house batteries because the generator starter is much smaller than a full size engine and its usually 2+ batteries sharing the burden.
 

jharrell

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Another interesting note about Lifeline batteries is it looks like they came out with their own LFP this year which I didn't notice, its very expensive relative to most other LFP's ($900+) but as always they have extremely good documentation on the battery and the BMS and it has Bluetooth monitoring.

In their docs for a 100ah battery they show 200 amps for 3 seconds, 300amps for 31 milliseconds, 440amps for 500 microseconds, 550 amps for 250 microseconds. This should handle starting with not much issue.

Very tempting a Lifeline has a legendary reputation in the lead acid world and my AGMs from them have served me very well although the price would be hard to swallow at nearly twice the Chin and others.

Would be great to see Will review one.

Check out the docs here for details:

https://lifelinebatteries.com/products/rv-batteries/ll-12v100-27/
 
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eXodus

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Another interesting note about Lifeline batteries is it looks like they came out with their own LFP this year which I didn't notice, its very expensive relative to most other LFP's ($900+) but as always they have extremely good documentation on the battery and the BMS and it has Bluetooth monitoring.

In their docs for a 100ah battery they show 200 amps for 3 seconds, 300amps for 31 milliseconds, 440amps for 500 microseconds, 550 amps for 250 microseconds. This should handle starting with not much issue.

https://lifelinebatteries.com/products/rv-batteries/ll-12v100-27/
those values are very close to or lower then CHINS , 280A for 5 seconds

For double the price of Lifeline, I would just buy two of the others. Gives me double the amperage.
Further double the wiring, more redundancy. Two parallel batteries with slightly lower specs are usually still better then one high end battery.
 

jharrell

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those values are very close to or lower then CHINS , 280A for 5 seconds

For double the price of Lifeline, I would just buy two of the others. Gives me double the amperage.
Further double the wiring, more redundancy. Two parallel batteries with slightly lower specs are usually still better then one high end battery.
Does Chins even document what it can do under 5 seconds? Most of the starter spike looks to be under 500 microseconds which is 440 amps in the Lifeline. I don't think I have seen a LFP that documents the BMS capabilities better than this Lifeline, this was similar on the AGM side where their documentation was extensive and trustworthy.

Same goes for build quality, I am going to guess the internals are way up there in robustness, I would love to see a teardown. You are right though not sure if its worth it at double the price not without more long term data on how they hold up, thats what sold me on spending nearly 2x a normal AGM was there well known reputation for lasting a very long time, if I purchased now I would most likely go with a Chins/Ampertime or equivalent.
 

circus

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5500w? I'm guessing about a 11hp engine. I just replaced the 6 year old battery in my 18hp lawn mower. On sale, the new battery was $20. Why not just buy a lawn mower starter battery? beats possibly harming something expensive.
 

jharrell

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5500w? I'm guessing about a 11hp engine. I just replaced the 6 year old battery in my 18hp lawn mower. On sale, the new battery was $20. Why not just buy a lawn mower starter battery? beats possibly harming something expensive.
I sorta agree, in re-reading see eXodus want to do a large 24-48v system in the future and this is just a stop gap. In that case I would probably get a small lead starting battery for the generator or more likely rewire the generator starter to the starting battery of the rv to keep it simple. Then in the future the large bank could have a dc-dc converter for 12v to charge from large bank and maybe another for 12v alternator charging to large bank (wish someone would make a two-way dc-dc charger).

This is one reason I prefer a 12v house system its much easier to interface with the chassis for alternator charging and vis versa for emergency starting and keeping chassis charged, also everything in the house is 12v (lights, thermostat etc.) So you probably need a mini 12v house system anyway. 12v does need larger conductors for high power (I have 4/0 for my 3000w inverter) and inverter pretty much top out at 3000w for 12v, but thats plenty for my 30ft Class A. Even a large 10kwh could be made 12v no problem, only issue is making sure the alternator can handle a discharged battery.
 
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