2x SOK 206Ah or 4x SOK 100Ah?

[jsalbre]

I'm building out a system with a Victron Multiplus II 2x120. My plan was to use a pair of SOK 206Ah (non-heated).

Min@SOK (and their product page) tells me that the BMS is rated for 130A continuous output, and this post has @jharrell saying they've pulled far higher continuous discharge rates, and charged them at well over the listed (50A) rate with no BMS cut-outs. 2400w/14v=200A, which is obviously less than the theoretical 130Ax2=260A rate. That tells me I should be fine, but then I see others posting here (and many on the SOK FB group) about struggling to run even smaller inverters off of two of these.

My order is supposed to ship out tomorrow so there's still time to change it. Should I be changing to 4 of the 100Ah SOKs instead? I'd really like to avoid the extra 18 pounds, $200, and considerably more physical space taken up by 4 batteries. If I have to switch to 100Ah then I'm going to be space-limited to 4. With the 206Ah I have space for a 3rd if I need more capacity in the future.

Thoughts?

 

[jsalbre]

Anybody? I realize I only asked this a couple hours ago and patience is a virtue and all, but I'm stressing out here about potentially needing to cancel or change my order before it ships and I get hit with huge shipping and restocking fees. Really hoping someone can come to my rescue.

Thanks all.

 

[rmaddy]

The MultiPlus you mention is 3000VA which is 2400W. 2400W / 12V / 90% = 222A. So your batteries need to support up to 222A continuously if you have a 2400W load.

I have 18 month-old SOK 12V 206Ah batteries that claim 100A max continuous. Based on what Min says the newer version supports 130A. If the newer version does support 130A then two will have no issue running your MultiPlus.

You might have an issue if you try to take full advantage of the surge capabilities of the inverter to briefly go well over 2400W. But if you stay under 2400W and if the newer batteries really support 130A each then you should be fine.

How often to you plan to go over 2000W? If you need to go that high on regular basis then 4 100Ah batteries may be better long term. If you will rarely use that much power then go with the 2 206Ah.

 

[jsalbre]

My main high amp draw will be a 15k BTU RV AC unit (Coleman Mach 8, 14A (1680W) normal, 18A (2160W) "desert conditions"). That will be the only large load when it's running on battery as that will only be when driving (batteries will be backed by 800W of solar and a 60A DC-DC). I ran the same system in a previous RV system I built up, but I had 6x 105Ah Lion Energy batteries in that, so the max current was never a concern. I honestly didn't even think about it. The idea is for my wife to be able to run things in the trailer if I'm not around without having to think about power usage (this worked fine for over a year full-time living in the last trailer). If the AC is running I don't want her to have to remember to shut it off before doing anything else.

 

[rmaddy]

A 2160W A/C is going to have a much larger startup surge. You might need to add a soft start to the A/C.

 

[jsalbre]

Sorry, should have mentioned that, I have a MicroAir EasyStart for it.

 

[jsalbre]

So would you stick with the 2x 206Ah or switch out to the 4x 100Ah?

Or there's option 3: Build my own "pair" of battery packs with JBD 150A BMS's? The ability to know I'll be good, plus the potential for $500+ in cost savings is tempting. I'm confident in my skill level with electronics and electrical work, but I'm hesitant to go this way as I've never built a pack before.

 

[time2roll]

2x 206 is my call

 

[rmaddy]

I've been happy with my SOK batteries. Given the 130A max continuous discharge rating I would go with the 2 206Ah (vs 4 100Ah) batteries since they can easily handle the 222A max that you will need for your inverter.

The choice of doing a DIY battery is up to you. Do you want to buy a pair of batteries and work on the rest of the RV or do you want to add another big project to your TODO list?

 

[jsalbre]

Ok, you guys (or girls?) have helped a lot. It's obvious my preference is for the 2x 206, so it's good to hear that you agree.

@rmaddy You're 100% correct on the DIY solution. I really don't have time to add another large project. I barely have enough time to get the current projects done.

Thanks all, you've prevented the minor panic attack my wife would have had when I told her I needed to modify my design again, potentially costing more $$.

Now to wait for Current Connected's shipment to arrive.

 

[jharrell]

A lot of people having issues with large inverters are because they are physically disconnecting and reconnecting the inverter on a regular basis which causes a large inrush on the inverter caps.

Also there are reports the new Bluetooth BMS is more sensitive to overcurrent than the old one. So even though I can run mine up 150 amps continuous and same with charge amps the new ones may trip right at the listed 130 amps and 70 amps charge (needs to be confirmed) and it may have lower surge limits as well.

60 amp DC-DC plus 800w solar will be running probably at least a 40-50 amp deficit which is ok you will have 10 hours but batteries will be discharged some when you arrive. If you run the AC fully off batteries it will run them 100-0 in under 3 hours and push them pretty hard get them pretty warm.

 

[jsalbre]

A lot of people having issues with large inverters are because they are physically disconnecting and reconnecting the inverter on a regular basis which causes a large inrush on the inverter caps.

Also there are reports the new Bluetooth BMS is more sensitive to overcurrent than the old one. So even though I can run mine up 150 amps continuous and same with charge amps the new ones may trip right at the listed 130 amps and 70 amps charge (needs to be confirmed) and it may have lower surge limits as well.

60 amp DC-DC plus 800w solar will be running probably at least a 40-50 amp deficit which is ok you will have 10 hours but batteries will be discharged some when you arrive. If you run the AC fully off batteries it will run them 100-0 in under 3 hours and push them pretty hard get them pretty warm.

I don’t plan to disconnect the inverter unless it dies. My last system it was turned on for nearly a full year with the only “disconnect” being when we managed to drain the batteries on an unusually long and hot travel day. Honestly

We used to get 7+ hours of A/C drive time with 60A DCDC and 600w solar on a 630Ah bank. We don’t plan to drive as long anymore and the new trailer is better insulated, so I think that’ll do fine. The only time the. A/C should be running fully off battery would be when we stop for gas, or maybe for a short burst when boondocking just to take the edge off.

I didn’t order the heated batteries, so I’m hoping they don’t have the new Bluetooth BMS, or if they do that some tweaking can be done to it. I suppose worst case I could always swap the BMS for something more tolerant if necessary. Seems like a waste on new batteries but it’s cheaper than return shipping and restocking fees. I’ll open mine up and get BMS pics when they arrive and try to do some testing if possible if they have the Bluetooth BMS.

 

[F29DCB]

Quick newbie question.
If I plan to run three 12v 206 ah SOK's in parallel for my new RV install.
Do all three need to be the bluetooth models?
or can I get Two non bluetooth and one with to save the extra cost on two of them?

 

[jsalbre]

Quick newbie question.
If I plan to run three 12v 206 ah SOK's in parallel for my new RV install.
Do all three need to be the bluetooth models?
or can I get Two non bluetooth and one with to save the extra cost on two of them?

All of them are Bluetooth now. Even the non-heated ones.

 

[F29DCB]

Thanks Jsalbre,
Good to know.
It doesn't make that very clear on their website.

 

[rmaddy]

All of them are Bluetooth now. Even the non-heated ones.

Is this true? Looking at the SOK website I see the older style with no Bluetooth and no heater or the newer ones with both.

Quick newbie question.
If I plan to run three 12v 206 ah SOK's in parallel for my new RV install.
Do all three need to be the bluetooth models?
or can I get Two non bluetooth and one with to save the extra cost on two of them?

Keep in mind that the Bluetooth only tells you about that one battery. I would say keep all three the same type. You either don’t need any Bluetooth or you need it with all three.

 

[jsalbre]

Is this true? Looking at the SOK website I see the older style with no Bluetooth and no heater or the newer ones with both.


Keep in mind that the Bluetooth only tells you about that one battery. I would say keep all three the same type. You either don’t need any Bluetooth or you need it with all three.

Yeah, they’re all using the same Bluetooth BMS now (it even has contacts for a heater). I just received a pair of 206Ah form the latest shipment last week. Personally I wish they were the old BMS as I’d prefer the higher discharge rate.

I agree on keeping the same type for all 3, it would be pointless to have Bluetooth on one and not the others.

 

[waveride]

Interesting. ti was not aware they all are using bluetooth. That is actually a problem for me. Is there a way to turn the bluetooth module off and still have the BMS function?

 

[jsalbre]

Interesting. ti was not aware they all are using bluetooth. That is actually a problem for me. Is there a way to turn the bluetooth module off and still have the BMS function?

Not that I’m aware of. I’ve heard of some people having luck getting SOK to send them one of the old non-BT BMS modules to swap out.

 

[time2roll]

Interesting. ti was not aware they all are using bluetooth. That is actually a problem for me. Is there a way to turn the bluetooth module off and still have the BMS function?

I would think if there was no app the phone will ignore. Or is this something else?