12v or 24v

Hi All

I could use some guidance. I have ordered 8 x 280 cells.

Goal - To power the caravan better. Install a 2500w inverter to run some general appliances, some very limited air con in short bursts.
Space - limited - required to run in a single long line.
Current Setup - van is all 12v, it has no inverter but has a couple of 240v applicances (Australia).

Originally my thought was to make a SINGLE 12v battery from them. then i was worried about balancing so though perhaps 2 x 280, now I am thinking would a single 24v battery, with a step down reducer be better for the 12v and lower current through the wires and BMS be best.

I wasnt sure of the best BMS option, weather to run the inverter off the batteries instead of though the inverter.

Thoughts? What would you do?

Over 1500W and 24v makes sense.
12V inverters go up past 3000 W, but need huge wires and fuses etc...
In a van, it may make the most sense to stick 12V...
maybe shop around for the inverter you like, then choose 12 or 24 from there.

What is your 12v requirements in the caravan power wise ? Maybe go for a 24v battery bank and 24v / 240v inverter. You would need an 8S BMS. Then power a switch mode power unit from the inverter for your 12v cct's. The 12v requirements in my caravan are minimal , restricted to lighting and water pump. Micro oven , TV , water heater , aircon and fridge freezer run of 240v 50Hz. I still want to do your conversion with the inverter to run stuff when off grid. Fridge and water heater can also run off LPG.

Following with interest.

Ryang said:

Hi All

I could use some guidance. I have ordered 8 x 280 cells.

Goal - To power the caravan better. Install a 2500w inverter to run some general appliances, some very limited air con in short bursts.
Space - limited - required to run in a single long line.
Current Setup - van is all 12v, it has no inverter but has a couple of 240v applicances (Australia).

Originally my thought was to make a SINGLE 12v battery from them. then i was worried about balancing so though perhaps 2 x 280, now I am thinking would a single 24v battery, with a step down reducer be better for the 12v and lower current through the wires and BMS be best.

I wasnt sure of the best BMS option, weather to run the inverter off the batteries instead of though the inverter.

Thoughts? What would you do?

Click to expand...

Whatever system voltage you choose the inverter basically has to be at system voltage.
Its just not reasonable to run a buck or boost converter from inverter voltage to system voltage.
Personally the biggest inverter I would run on 12 volts is ~2400 watts.
My rule is slightly arbitrary and 2500 watts@12 volts is doable.
If you go for a 12 volt system you could make 2 12 volt batteries each with its own commodity bms and parallel them on the system side of the bms.

As Supervstech with 12V systems the generally accepted max is not more than 2,000 Watts (non surge), simply because at that stage your running into very heavy wiring, fuses etc due to the amperage being pulled by the inverter. Quick Math: 12VDC @ 1,000 Watts = 120 Amps but at 24VDC that's only 60 Amps. There is no problem running 24V battery bank & inverter to provide your 230V 50Hz. (Australia) to run normal devices & appliances.

The really critical parts if your doing so is where many trip on the details.
- You will need a "Good, Reliable" 24V to 12V downstep converter (not a cheap buck converter) that will handle the amperages demanded by all the 12V equipment in your vehicle.
- Will you be wanting to charge via Solar Power and/or "Shore Power" which can be grid or gen-set ?

BMS choices will depend on which voltage you're going with due to the amperage handling it will need. Obviously, if you're going to stick to 12V you'll need to handle higher amperages for normal use things. For example, a coffee maker @ 1100W and we all need our morning coffee right... There are MANY choices & options and that can be somewhat confusing. For a simpler system, a respectable Smart BMS with Bluetooth capability runs around $100-$150 USD and several people use these here with great success. It all depends on how much you want to tinker & play with your gear, many prefer to set it up and then forget it but I personally like to keep an eye on everything. There are a few long running threads on Good Smart BMS' with Bluetooth and others as well.

Thanks gents For taking the time to reply.

My concerns are:
So in terms of battery cell setup, having 8 cells in a single line in a 24v setup, is this still going to charge all cells in balance? The same issue would be there for a 12v, 8 cell 560amp setup. But 2x 280 would only be 4 cells in each.
Not sure if this is a valid concern.

I have a Victron ip22 12/30 charger. I guess I’d just sell this and find an inverter charger combo perhaps.

I saw a nice Victron on 24 12v 20amp reducer. This looked good. My 12v load is always under 20amps.

I have a crappy renogy rover 40 charger which I am upgrading to a Victron 100/50. I’m convinced the renogy is faulty but their support is so difficult to work with. The product is just awful.

I use A backup 2400 Westinghouse generator for off grid. But the goal is 99% solar. We are off grid most of the time .

The main reason for the higher inverter is to run a load on the washing machine and in very limited time, run the air con. Have a full manual flair espresso coffee machine so no need for power here. It’s brilliant, can highly recommend! I was keen on the one Steve brought from aliexpress but if I go 24v I’ll do a combo charger.

Ryang said:

Thanks gents For taking the time to reply.

My concerns are:
So in terms of battery cell setup, having 8 cells in a single line in a 24v setup, is this still going to charge all cells in balance? The same issue would be there for a 12v, 8 cell 560amp setup. But 2x 280 would only be 4 cells in each.
Not sure if this is a valid concern.

I have a Victron ip22 12/30 charger. I guess I’d just sell this and find an inverter charger combo perhaps.

I saw a nice Victron on 24 12v 20amp reducer. This looked good. My 12v load is always under 20amps.

I have a crappy renogy rover 40 charger which I am upgrading to a Victron 100/50. I’m convinced the renogy is faulty but their support is so difficult to work with. The product is just awful.

I use A backup 2400 Westinghouse generator for off grid. But the goal is 99% solar. We are off grid most of the time .

The main reason for the higher inverter is to run a load on the washing machine and in very limited time, run the air con. Have a full manual flair espresso coffee machine so no need for power here. It’s brilliant, can highly recommend! I was keen on the one Steve brought from aliexpress but if I go 24v I’ll do a combo charger.

Click to expand...

Most combo chargers are low frequency, so they handle surge loads much better. Another reason to lean for 24v.

Ryang said:

Thanks gents For taking the time to reply.

My concerns are:
So in terms of battery cell setup, having 8 cells in a single line in a 24v setup, is this still going to charge all cells in balance? The same issue would be there for a 12v, 8 cell 560amp setup. But 2x 280 would only be 4 cells in each.
Not sure if this is a valid concern.

I have a Victron ip22 12/30 charger. I guess I’d just sell this and find an inverter charger combo perhaps.

I saw a nice Victron on 24 12v 20amp reducer. This looked good. My 12v load is always under 20amps.

I have a crappy renogy rover 40 charger which I am upgrading to a Victron 100/50. I’m convinced the renogy is faulty but their support is so difficult to work with. The product is just awful.

I use A backup 2400 Westinghouse generator for off grid. But the goal is 99% solar. We are off grid most of the time .

The main reason for the higher inverter is to run a load on the washing machine and in very limited time, run the air con. Have a full manual flair espresso coffee machine so no need for power here. It’s brilliant, can highly recommend! I was keen on the one Steve brought from aliexpress but if I go 24v I’ll do a combo charger.

Click to expand...

One concern about the combo chargers that was expressed by several people here and by Will on his 24V DiY system build video(), is they have a high standby draw, may not be a concern for you if you only have the need for aircon and can manually control when you power on the inverter, but if you have other a/c devices that need to be left on then it's something to consider. This may only apply for the MPP charger/inverters, but I have no direct experience.

Supervstech said:

Most combo chargers are low frequency, so they handle surge loads much better. Another reason to lean for 24v.

Click to expand...

Sounds good !

Excellent advise

considering I am basically starting again maybe a combo box would be the most cost effective.

I do like to closely monitor my equipment but it will be out of site under The seating area.

does anyone have any good 24v all in one recommendations th at have decent wifi/Bluetooth monitoring?
Thanks in advance

I am basically doing the exact setup you are, 8 280ah cells, 3000w inverter. I chose to go with the 24v setup using a Victron 24/3000 combo inverter charger. It has multiple AC inputs so I can switch between shore and generator, and the 3000w is low frequency and can boost to 6000w for several minutes rather than a few milliseconds like many others. I also went with the Victron 24-12 70a converter to run my 12v needs. For the BMS I went with the Chargery 8t, but plan to switch to the ElectroDacus when the new ones are out in August. I plan to also add solar soon.

JTrigger said:

I am basically doing the exact setup you are, 8 280ah cells, 3000w inverter. I chose to go with the 24v setup using a Victron 24/3000 combo inverter charger. It has multiple AC inputs so I can switch between shore and generator, and the 3000w is low frequency and can boost to 6000w for several minutes rather than a few milliseconds like many others. I also went with the Victron 24-12 70a converter to run my 12v needs. For the BMS I went with the Chargery 8t, but plan to switch to the ElectroDacus when the new ones are out in August. I plan to also add solar soon.

Click to expand...

Thats a great setup. Unfortunately i cant afford the $2000 (Aussie) for the Victron inverter combo. It would otherwise be my first choice.

Thanks for sharing

JTrigger said:

I am basically doing the exact setup you are, 8 280ah cells, 3000w inverter. I chose to go with the 24v setup using a Victron 24/3000 combo inverter charger. It has multiple AC inputs so I can switch between shore and generator, and the 3000w is low frequency and can boost to 6000w for several minutes rather than a few milliseconds like many others. I also went with the Victron 24-12 70a converter to run my 12v needs. For the BMS I went with the Chargery 8t, but plan to switch to the ElectroDacus when the new ones are out in August. I plan to also add solar soon.

Click to expand...

Same for me. 8 280Ah cells, 24V 8S, Victron Multiplus 3000/24, Electrodacus.

One thing I will add about the title of this thread 12V or 24V is the effect on wire size. Wiring size is actually a bigger deal than you may first think. Not only do you have half the current, but also twice the voltage. That means that you benefit both from the wire carrying 1/2 the current, plus any resistive losses on that lower current will also be half the % of 24V. So if you have long runs that are voltage limited not ampacity limited, then you can actually run 1/4 the wire size. That is 6 full AWG lower.

Example: Go plug the following into the Blue Sea Circuit Wizard, they are the same power:
12V, 100A, 10 feet, 1% -> 0AWG
24V, 50A, 10 feet, 1% -> 6 AWG

If you price heavy guage copper, it is not cheap. Plus the difficulty of routing. Heavy guage wire needs larger radius bends. And if you are talking 3000W, you are getting to 4/0 or even two in parallel. A victron Multiplus 3000 will do 6000W surge for 2 full minutes. That is 500A at 12V and while it may not blow a 400A Class T fuse (the largest size) it is really stretching the limit.

I originally planned 12V but realized since I was starting from scratch in the van I'm building, now is the time to go with 24V. Most things are available in 24V or 12V and if you go 24V up front no problem. Otherwise a big switching cost to do it later, and you never will.

Airtime said:

Same for me. 8 280Ah cells, 24V 8S, Victron Multiplus 3000/24, Electrodacus.

One thing I will add about the title of this thread 12V or 24V is the effect on wire size. Wiring size is actually a bigger deal than you may first think. Not only do you have half the current, but also twice the voltage. That means that you benefit both from the wire carrying 1/2 the current, plus any resistive losses on that lower current will also be half the % of 24V. So if you have long runs that are voltage limited not ampacity limited, then you can actually run 1/4 the wire size. That is 6 full AWG lower.

Example: Go plug the following into the Blue Sea Circuit Wizard, they are the same power:
12V, 100A, 10 feet, 1% -> 0AWG
24V, 50A, 10 feet, 1% -> 6 AWG

If you price heavy guage copper, it is not cheap. Plus the difficulty of routing. Heavy guage wire needs larger radius bends. And if you are talking 3000W, you are getting to 4/0 or even two in parallel. A victron Multiplus 3000 will do 6000W surge for 2 full minutes. That is 500A at 12V and while it may not blow a 400A Class T fuse (the largest size) it is really stretching the limit.

I originally planned 12V but realized since I was starting from scratch in the van I'm building, now is the time to go with 24V. Most things are available in 24V or 12V and if you go 24V up front no problem. Otherwise a big switching cost to do it later, and you never will.

Click to expand...

Very true. and another very nice setup.

What BMS (if you used one) did you go with?

What do you guys think of these?

specifically the SPF 3000TL HVM-24

It seems to tick all the boxes.

Odd that it only supports lead acid.

Supervstech said:

Odd that it only supports lead acid.

Click to expand...

Good Pickup

The 2 next to it say Li/LA, and it doesnt. I missed that!

epever also make a hybrid. not sure it supports LI. otherwise the specs look good.

Samlex, Xantrex, and Magnum also make inverter/chargers.

BoloMKXXVIII said:

Samlex, Xantrex, and Magnum also make inverter/chargers.

Click to expand...

Unfortunately they are all out of budget. I’d buy the Victron in that price range. Not necessarily cause it’s better, but because I’ve used their products and really like them

https://mppsolar.en.alibaba.com/pro...A_mppt_solar_charger_battery_charger_60A.html

This looks cool. Wasn’t sure I’d find a mpp in 230v.

This looks cool. Removable lcd display screen to mount in the van and phone connectivity

Does it seem to tick all the boxes?

Ryang said:

What BMS (if you used one) did you go with?

Click to expand...

Electrodacus SBMS0. It directly controls inverter and charger, no big high current switches required. A bit more of an advanced user setup, not for everyone. With many inverters and chargers you may need to hack some power switches. However, it does integrate very nicely with Victron products out of the box as they in general provide remote control and are the only inverter/chargers that provide separate remote on/off control for inverter and charger. Very simple--connect two signal wires for inverter, two for charger, install the right SW and it works--BMS control.

Airtime said:

Same for me. 8 280Ah cells, 24V 8S, Victron Multiplus 3000/24, Electrodacus.

One thing I will add about the title of this thread 12V or 24V is the effect on wire size. Wiring size is actually a bigger deal than you may first think. Not only do you have half the current, but also twice the voltage. That means that you benefit both from the wire carrying 1/2 the current, plus any resistive losses on that lower current will also be half the % of 24V. So if you have long runs that are voltage limited not ampacity limited, then you can actually run 1/4 the wire size. That is 6 full AWG lower.

Example: Go plug the following into the Blue Sea Circuit Wizard, they are the same power:
12V, 100A, 10 feet, 1% -> 0AWG
24V, 50A, 10 feet, 1% -> 6 AWG

If you price heavy guage copper, it is not cheap. Plus the difficulty of routing. Heavy guage wire needs larger radius bends. And if you are talking 3000W, you are getting to 4/0 or even two in parallel. A victron Multiplus 3000 will do 6000W surge for 2 full minutes. That is 500A at 12V and while it may not blow a 400A Class T fuse (the largest size) it is really stretching the limit.

I originally planned 12V but realized since I was starting from scratch in the van I'm building, now is the time to go with 24V. Most things are available in 24V or 12V and if you go 24V up front no problem. Otherwise a big switching cost to do it later, and you never will.

Click to expand...

What solar panels and what is watts per panel and voc for your 24v system. Wanting the go 24v but trying to save on cost on mppt. It’s the start up voltage on the mppt and 24v battery thats wanting me to stay at 12v system. Ty

DrIns said:

What solar panels and what is watts per panel and voc for your 24v system. Wanting the go 24v but trying to save on cost on mppt. It’s the start up voltage on the mppt and 24v battery thats wanting me to stay at 12v system. Ty

Click to expand...

Curious why you are concerned about startup voltage? Unless you plan to run them all in series in one string at higher voltage, which I wouldn't recommend. Shade on just part of any one panel will shut down the whole string. I have 2 parallel strings of 2 in series. One pair at the front of the van and one pair at the rear. If one is shaded, the other pair still works.

I have Renogy 160D-SS panels, 160W each, Voc is 22.9V. Total Voc for my setup is 45.8V.