Lithium battery upgrade on 17B

[dosby]

I got 100Ah GoPower battery from ETI as part of their full lithium package, and it serves the basic needs, but I would like more flexibility with non-hookup camping. Water supply is usually not a big deal and can be solved by a 100-150ft collapsible hose. Drainage issue is partially solved by washing dishes/hands/kids outside. However, we did deplete the battery completely a couple of times when camping in a shade and using microwave/instant pot. Trying to avoid non-hookup sites since then. I know that portable solar could help recharge but not in a shade or a completely forested campground.
What I am thinking is that adding a 300Ah battery could help us last 3-4 days. A single 300Ah battery, to avoid complex wiring. And it's not heavy enough to break my back, ~55-65 lb.
The only place to install it is under the passenger (right) side bench. We have an exterior hatch, for mostly lighter smaller things like levelers, etc. A grill won't fit, not even a front box. All in all, I am ready to sacrifice some interior space. Driver side space is mostly full - there is a water heater tank, electrical stuff, water pump, etc.

I have found a few 300Ah choices online - most of them are ~21" * 10" * 10". There are a few that are 15" * 7" * 9" and would fit the space better but those don't have much customer reviews and seemed to be made via some "pouch" technology (totally legit, just not as tested in RVs). Example - https://www.amazon.com/dp/B0CX1DGZ29
Just 55 lb and smaller than others. What do you all think?

Another question is what to do with the old battery. I read some folks remove it completely, pull the existing wires and reuse them for a new battery. I am thinking maybe keep it as a back up battery? And install some 1-2-OFF 3-way switch? I would probably have to 1-2 switch not just the thick inverter cables but also the 10AWG charging cables, too? And I would need to just keep the backup battery charged, i.e. charge it every few months. Is it worth the hassle?
I know that running 300Ah and 100Ah in parallel would not be a good idea.

The space under the passenger bench has an inverter, but otherwise is empty. Where would you place the new battery? I am thinking either the very back (basically almost directly above the existing battery) or close to the wheelwell (better for weight distribution).

[dosby]

pictures, set 1

[dosby]

pictures, set 2

[dosby]

The space in the back is 19"W but floor space is just 15"W - it would be closer to the existing battery wires. Only the "pouch" battery would fit there, if put lengthwise.
The space near the wheelwell (where the white cap with sanitizer stuff bucket and the red levelers are) is 12"W and ~20"L to the inverter.
So, a perfect size for my new battery would be 12"W, or 15"W, and not very long, but unfortunately, they don't make them square for some reason
There is one, actually - https://www.amazon.com/GuaiGLong-12V.../dp/B0CB12S64R, but it's more $$$

There is also dual-battery route - https://www.amazon.com/ECO-WORTHY-Ba.../dp/B0BJZKC5WN
But 2 of them are 82 lb VS 55 lb for the "pouch" one.

[dosby]

Does anyone know what kind of 12A plugs the inverter uses? If I keep the current battery for backup, I would need to detach the inverter cables from those plugs and connect them to the 1-2-OFF switch. I could not find the way to unplug them but I probably just didn't pull hard enough.

Another idea is to find a new battery that would fit the existing group 27 box. It won't be 300Ah, but maybe 200Ah?
BTW, current 100Ah battery is 36 lbs, 12.9L x 6.8W x 9.2H
Compare to 300Ah, 55 lbs, 13.58"L x 7.48"W x 9.64"H - https://www.amazon.com/dp/B0CXSP94H4

[rubicon327]

Personally I would do one new, high quality battery as big as I could fit and not worry about paralleling an older one. Check out the SOK 280 AH…
https://www.us.sokbattery.com/produc...-and-bluetooth

There is also a 300AH battery from Epoch which is a brand I recently became aware of from forum member viator36
https://www.currentconnected.com/pro...ch-essentials/

This is the 400AH Bestgo that we use that has been great…
https://www.electriccarpartscompany....-battery-packs

[dosby]

Originally Posted by rubicon327

Personally I would do one new, high quality battery as big as I could fit and not worry about paralleling an older one. Check out the SOK 280 AH…
https://www.us.sokbattery.com/produc...-and-bluetooth

This one is a good form factor and the price is not bad either. Thanks! A bit heavier than I would want, it's probably not a "pouch" battery.

Originally Posted by rubicon327

There is also a 300AH battery from Epoch which is a brand I recently became aware of from forum member viator36
https://www.currentconnected.com/pro...ch-essentials/

This one looks very similar in size/weight to the one I found for $520, but with blue tooth and heating.

Originally Posted by rubicon327

This is the 400AH Bestgo that we use that has been great…
https://www.electriccarpartscompany....-battery-packs

400Ah is a future proof choice for sure, but ~100 lbs and $1.5k
Can't justify the cost, not at the moment, at least.

I wonder if heating would become more of an issue than a feature. Blue tooth feature is nice, my current controller is only reliable for voltage, not state of charge. I wonder how the measure it internally within the battery, some sort of Watts + Voltage combination? The controller knows only current Voltage...

[rubicon327]

Originally Posted by dosby

Blue tooth feature is nice, my current controller is only reliable for voltage, not state of charge. I wonder how the measure it internally within the battery, some sort of Watts + Voltage combination? The controller knows only current Voltage...

They probably have a shunt within the battery that measures all current in and out. My Bestgo with integral monitor on the casing uses a setup similar to a Victron BMV-712 but a cheaper version. I still have a Victron display mounted on cabinet face to view SOC. It’s typically very close to the monitor on the battery.

[dstreight]

If you have a modicum of electro-mechanical skills and/or can follow directions maybe consider building your own battery.

4 of these in series plus a BMS: https://www.ebay.com/itm/145611152404
https://www.ebay.com/itm/11596739007...904818XJ8624XM

Big bang for the buck and you get to configure the form factor. I did the same 4+ years ago using Fortune Prismatic cells to build my 400A battery and its been fantastic for our all electric 15A.

But, and you've probably thought this one through...bigger battery will need either more hours from your re-charge source, more current or both.

[rubicon327]

Originally Posted by dosby

Does anyone know what kind of 12A plugs the inverter uses? If I keep the current battery for backup, I would need to detach the inverter cables from those plugs and connect them to the 1-2-OFF switch. I could not find the way to unplug them but I probably just didn't pull hard enough.

If you are speaking about the DC connections (12 volt (V) not amp (A)) on the inverter you need to remove the red and black plastic terminal covers with two phillips head screws each, slide them down the wire and then the ring terminal connections will be exposed. These can then be removed with a wrench.

[dosby]

Originally Posted by rubicon327

If you are speaking about the DC connections (12 volt (V) not amp (A)) on the inverter you need to remove the red and black plastic terminal covers with two phillips head screws each, slide them down the wire and then the ring terminal connections will be exposed. These can then be removed with a wrench.

Thanks!
Although now I think the backup battery is not a good idea, it's better to have just a good battery monitor. I lost faith in them with the stock ETI installation but it looks like it could be just a $20 shunt system on top of any battery, with a wired screen.

[dosby]

Originally Posted by dstreight

If you have a modicum of electro-mechanical skills and/or can follow directions maybe consider building your own battery.

4 of these in series plus a BMS: https://www.ebay.com/itm/145611152404
https://www.ebay.com/itm/11596739007...904818XJ8624XM

Big bang for the buck and you get to configure the form factor. I did the same 4+ years ago using Fortune Prismatic cells to build my 400A battery and its been fantastic for our all electric 15A.

But, and you've probably thought this one through...bigger battery will need either more hours from your re-charge source, more current or both.

That is very educational, thank you! Makes you think why the batteries are so much larger than the combined volume of the cells. Looks like I could easily fit 300Ah in the existing group 27 battery box, and with a slightly bigger weight. Makes me want to disassemble the 100Ah GoPower stock battery. Some day.
The prices are not dirt cheap, though. For a moment, I thought it was $160 for 4 304Ah cells, but no It's the same $550 or so I found on Amazon for the already completed battery. Maybe the cell grading/quality is different, who knows.
I would think that the cost of the rest of the stuff, BMS, busbars, and the box is very cheap. Using bus bars would limit the form factor flexibility, but still, the combined total is significantly smaller than that of the pre-made batteries, in both weight and dimensions.

[dosby]

The simplest shunt I could use for 300Ah and probably easily install would be something like this?
https://www.amazon.com/dp/B07T9LV66P
My draw is limited by the ETI inverter - I believe it's 100A max for a constant load.

[Perry Butler]

Originally Posted by dosby

The simplest shunt I could use for 300Ah and probably easily install would be something like this?

https://www.amazon.com/dp/B07T9LV66P

My draw is limited by the ETI inverter - I believe it's 100A max for a constant load.

Shunts in that price range lack the one thing we need from a shunt. History.

Personally what you linked is merely a fancy battery monitor. It works great as long as nothing is wrong with your system. When something goes wrong you have no info. I want a shunt with history to give me an idea what happened.

For example, when our WFCO decided to charge our AGM batteries at 20.37 volts they were fried. Our Victron BMV-712 shunt told me the 20.37 volt charge in its history. I researched on the Internet and found others who also had their batteries fried by their WFCO. Without history, I wonder how many other batteries would have been fried before we found out our WFCO's issues.



There's a reason some things are cheap. You spent all that money on your camper, so a cheap shunt to identify a problem is not the place to pinch pennies. Get a shunt with history, such as a Victron Smart Shunt, or my choice, a Victron BMV-712. That BMV-712 saved me a minimum of another set of failed batteries, and easily paid for itself. What if I had fried three sets of batteries before I found the issue? There is nothing wrong with money spent wisely.

Food for thought,

Perry

[hugh]

I went with the "build them yourself" lithium batteries for my 21C. I built a couple of 460Ah batteries (920Ah total) for around $2150. I haven't looked at recent prices for the cells, but i don't think they've changed that much.

Some more info here:

https://www.escapeforum.org/forums/f...tes-23522.html

[John in Santa Cruz]

I've been very happy with the 2*206AH SOK batteries I installed a couple years ago. 5200 watt*hours usable power. 360 Watt solar panel can fully charge them from a total deep discharge in 2 good days.

[dosby]

Originally Posted by Perry Butler

Shunts in that price range lack the one thing we need from a shunt. History.

...

Get a shunt with history, such as a Victron Smart Shunt, or my choice, a Victron BMV-712. That BMV-712 saved me a minimum of another set of failed batteries, and easily paid for itself. What if I had fried three sets of batteries before I found the issue? There is nothing wrong with money spent wisely.

Food for thought,

Perry

Right, the one I referred to says no SOC measurement possible in its reviews. I can already see the battery voltages on my ETI monitor under the bench. Why do they have a shunt and not measure SOC correctly, that's weird.

Anyway, looks like these 2 may work to monitor correct SOC:

https://www.amazon.com/dp/B0C6K4J7Q4

https://www.amazon.com/dp/B08V1VZNGH

[dosby]

For my 17B, I don't think I need more than 300-400Ah. There is simply no space or weight capacity. I know that one 300Ah battery nowadays weighs less than one 6V lead-acid that ETI used to install in pairs in the back of the trailer, but I guess I could find something else to carry other than excessive batteries.
I only have 180W solar and ~10A DC-DC from the vehicle, so recharging a big bank would only be possible via shore power.
Not planning to run A/C (this is WA). May switch to compressor fridge in the future but I like how quiet my absorption one is. If it dies, I would think about a compressor one. My goal is essentially to be able to camp without shore power for 3-4 days at most, in forested areas, with occasional microwaving and instant potting.

[Perry Butler]

Originally Posted by dosby

Right, the one I referred to says no SOC measurement possible in its reviews. I can already see the battery voltages on my ETI monitor under the bench. Why do they have a shunt and not measure SOC correctly, that's weird.

Anyway, looks like these 2 may work to monitor correct SOC:

https://www.amazon.com/dp/B0C6K4J7Q4

https://www.amazon.com/dp/B08V1VZNGH

These are just another set of cheap battery monitors. They work fine as long as you don't have an issue. Read my previous posts again.

Pay me now, or pay me later,

Perry

[dstreight]

^^^ agree with the '...cry once...pay me now or pay me later' philosophy. All my Victron gear, 10-years+ collecting this/that, has been reliable and worth the extra cost IMHO. Not to mention the network ability with staying in the Victron family of equipment.