Combining technologies

[emeraldcoastcamper]

I have (2) three year old Crown 6V AGMs connected as 12V, and don't want to just discard them. Can I safely string a Battleborn or similar Lithium onto the Crowns? If so which battery should be first in the line? I read that Goal Zero has a connector for doing this but you have to buy their "battery Bank" system.

 

[Geriakt]

Not a wise idea to mix chemistries. The LA has a much higher resistance and also needs to increase voltage to charge at colder temps. You will either never get a charge on the LA or cook your LiFepo.
Do yourself a favor and toss the $100s of LA to protect the $1000 BB.

You know the saying penny wise, pound foolish

 

[emeraldcoastcamper]

Thank you for the reply. I was expecting this to be the case. I actually would need two BBs to approximate what I would give up with the Crowns. They are 220AH which gives me 110AH usable. I understand the BB 100 Amp batteries yield 80AH usable. I'll stick with the AGM Crowns for a while and hope LI prices come down and I can make a DIY battery. Looks pretty straightforward from all the Youtube vids.

On another note there are Tesla battery packs for sale at $1400 for a 5KW brick. That is intriguing.

 

[Steve_S]

I have (2) three year old Crown 6V AGMs connected as 12V, and don't want to just discard them. Can I safely string a Battleborn or similar Lithium onto the Crowns? If so which battery should be first in the line? I read that Goal Zero has a connector for doing this but you have to buy their "battery Bank" system.

If you want to run both, you'll have to isolate them with a switch so your either running the AGM's or LFP but not both. Then you have to consider the charging aspect and even with BB's you still have to be within a certain spec for them, a 2 stage charging process.

Tesla Packs are not LFP and that is even more persnickety and their voltage range has to be adjusted for. DIY is likely the better option, you can make a 200 / 300 or even 400AH 12V pack. 200AH cells can be had for as low as 71 USD ea, 4 cells = 12V plus BMS & Shipping

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Catl Lishen 3.2v Lifepo4 202ah Lithium Batteries 3.2v Lifepo4 200ah Battery For Ess,Off Grid,Home Solar Energy - Buy Catl,3.2v Lifepo4,200ah Lifepo4 Product on Alibaba.com

deligreen.en.alibaba.com

EDIT: Adding switch link

e-Series - Blue Sea Systems

350 Amps continuous rating for inboard gasoline or diesel engines.

www.bluesea.com

 

[emeraldcoastcamper]

Thanks Steve. I am placing an order for 4 of these CATL batteries. If they work out I will order another 4. Now I just need to source a good BMS and the connector plates. Would the experts here suggest an enclosure, or is double side tape enough? They will reside in a storage drawer in the sofa of our trailer.

 

[Steve_S]

Deligreen is closed till Feb.01 due to the holidays.
They will add eh busbars to assemble the cells (extra but like $2 ea or so).

A really great set of reads here: http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/

You'll need to FUSE each pack, I like the MRBF type for ease & simplicity (125% of the output capacity is usual)

Bay Marine – Marine Rated Battery Fuse and MRBF Single Fuse Holder Kit – 30-300A | eBay

Choice of Fuse Sizes Available: 30A, 40A, 50A, 60A, 75A, 80A, 90A, 100A, 125A, 150A, 175A, 200A, 225A, 250A, 300A. Fuse Size List Ignition Protected – Safe for installation aboard gasoline powered boats.

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Will Prowse has found a lower cost BMS with Cold Temp cutoff for something like $80 but I'm not sure which is which now as there seem to be a couple but they have different software so I'm not sure. There is a couple of threads on it.

Look at Will's videos on assembling a 12V pack, not hard to do, a casing of some sort is not a bad idea, you do not want anything being able to touch the tops of the cells in the pack, not even a stray rodent. A metal box can be used as long as there is a "non-conductive" liner, some folks here found plastic battery boxes for such out of China, quite reasonably priced and some that are way out there in price.

 

[emeraldcoastcamper]

Deligreen is closed till Feb.01 due to the holidays.
They will add eh busbars to assemble the cells (extra but like $2 ea or so).

A really great set of reads here: http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/

You'll need to FUSE each pack, I like the MRBF type for ease & simplicity (125% of the output capacity is usual)

Bay Marine – Marine Rated Battery Fuse and MRBF Single Fuse Holder Kit – 30-300A | eBay

Choice of Fuse Sizes Available: 30A, 40A, 50A, 60A, 75A, 80A, 90A, 100A, 125A, 150A, 175A, 200A, 225A, 250A, 300A. Fuse Size List Ignition Protected – Safe for installation aboard gasoline powered boats.

www.ebay.com

Will Prowse has found a lower cost BMS with Cold Temp cutoff for something like $80 but I'm not sure which is which now as there seem to be a couple but they have different software so I'm not sure. There is a couple of threads on it.

Look at Will's videos on assembling a 12V pack, not hard to do, a casing of some sort is not a bad idea, you do not want anything being able to touch the tops of the cells in the pack, not even a stray rodent. A metal box can be used as long as there is a "non-conductive" liner, some folks here found plastic battery boxes for such out of China, quite reasonably priced and some that are way out there in price.

Thank you so much. Yeah, when I placed the order I got a message they are closed for New Year.

 

[Geriakt]

Thanks Steve. I am placing an order for 4 of these CATL batteries. If they work out I will order another 4. Now I just need to source a good BMS and the connector plates. Would the experts here suggest an enclosure, or is double side tape enough? They will reside in a storage drawer in the sofa of our trailer.

again not the best idea to mix older used Lifepo with new ones. Do it all at one time so they are matched. Yes it can be done but if the older ones are limited in power, your new ones will also be limited in power.

I am using two Teslas in parallel, but i needed to do a lot of engineering to make them safe with external BMS systems. Teslas are not a beginner's battery system but the sure are low cost for the power they provide.

 

[Steve_S]

again not the best idea to mix older used Lifepo with new ones. Do it all at one time so they are matched. Yes it can be done but if the older ones are limited in power, your new ones will also be limited in power.

I am using two Teslas in parallel, but i needed to do a lot of engineering to make them safe with external BMS systems. Teslas are not a beginner's battery system but the sure are low cost for the power they provide.

IF they are within their own packs with their own BMS, it is moot. LFP charge profiles remain the same.
You thinking like it's FLA / AGM, it is NOT. All the cells "within a pack" should match up, so all 200AH or 100AH but never mixed like 3x100AH + 2x50AH to make a 400AH pack would fail miserably.

 

[emeraldcoastcamper]

Thanks for the reply. I understand what you are saying about matching. I would order the second set of cells immediately after I determine the first bunch are "as advertised" so there probably won't be more than a few AH used. Looking for suggestions on large draw (150) AH BMS.

 

[emeraldcoastcamper]

again not the best idea to mix older used Lifepo with new ones. Do it all at one time so they are matched. Yes it can be done but if the older ones are limited in power, your new ones will also be limited in power.

I am using two Teslas in parallel, but i needed to do a lot of engineering to make them safe with external BMS systems. Teslas are not a beginner's battery system but the sure are low cost for the power they provide.

I am liking the Tesla packs for my home solar system which is Grid tied now with 5.5KW PV. The Tesla packs would give me a backup in the event of a long term grid failure. My LIfePO project is just for the Airstream to replace the AGMs.

 

[Geriakt]

Thanks for the reply. I understand what you are saying about matching. I would order the second set of cells immediately after I determine the first bunch are "as advertised" so there probably won't be more than a few AH used. Looking for suggestions on large draw (150) AH BMS.

if that is the case you will have no issues

 

[emeraldcoastcamper]

 

[emeraldcoastcamper]

if that is the case you will have no issues

 

[emeraldcoastcamper]

With the goal in mind to add a LifePo 200 amp, and retain the existing Crown AGMs what about putting the LifePo first in line from the Charger with a Diode between the LifePo and the AGMs?. I can set the charge profile for the Lithium to protect it yet still have the AGMS on board. They are heavy and strange as it may sound I need the extra weight in the front of my Airstream for tongue weight. Of course I can just disconnect and leave them as ballast but the reserve power would be nice to have.

 

[cass3825]

Looking for suggestions on large draw (150) AH BMS.

Take a look at the Chargery BMS. Options up to 600A. http://chargery.com/BMS8T.asp

 

[grizzzman]

I run my CG2 bank with my
LFP bank during camping and guess what? The world did not explode!
The LFP will do most of the work. Remember that LFP has a higher rested voltage. As such the CG2 bank will simply be "tickle charged" during the night. Due to the lower resistance of The LFP will take the brunt of the charging. I put a 100 amp fuse on CG2 and a volt/amp meter. I observed for myself the relationship between the two chemistries . An added bonus that I observed, was load sharing at high loads. And as an added bonus, if the BMS disconnects any sensitive equipment does not get spiked voltage from the charging side. Would I suggest to someone to do this? All that I can say is do your homework. If you are willing to keep an eye on things that for "me" is no big deal. Ok nah sayers have at it.

 

[emeraldcoastcamper]

What is CG2? I’m new to this so please forgive my ignorance. I am the OP and still working through leaving my AGMs in place when I add the Lifepo. I was of the same mind as you. Make the Lifepo primary with a charge profile to suit. I may put a battery switch in to isolate the two chemistries but is that really necessary. My cells are on order and as soon as the Lunar holiday is over maybe they will ship.

 

[ghostwriter66]

What is CG2? I’m new to this so please forgive my ignorance. I am the OP and still working through leaving my AGMs in place when I add the Lifepo. I was of the same mind as you. Make the Lifepo primary with a charge profile to suit. I may put a battery switch in to isolate the two chemistries but is that really necessary. My cells are on order and as soon as the Lunar holiday is over maybe they will ship.

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Buy Duracell Golf Car Battery, Group Size GC2 : Golf Cart Batteries at SamsClub.com

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[ghostwriter66]

What is CG2? I’m new to this so please forgive my ignorance. I am the OP and still working through leaving my AGMs in place when I add the Lifepo. I was of the same mind as you. Make the Lifepo primary with a charge profile to suit. I may put a battery switch in to isolate the two chemistries but is that really necessary. My cells are on order and as soon as the Lunar holiday is over maybe they will ship.

So YES you can string them all together but depending on the battery you set the SCC to, you will either over charge one set or undercharge the other ... ALSO - with LFP we run our abtteries down to 10% with zero issues BUT if you have them strung with WET CELLS or AGM then you have to be constantly monitoring the AGMs to make sure you not below 50% ....

The way we did it until we finally got rid of our legacy systems was initially had one BANK of solar panels that fed 2 SCC through an A/B switch ... We also had a bank of LFP batteries and a Bank of GC2 also controlled to the inverter by an A/B switch ... And a battery meter with an A and B input connected to both. SO we would always charge the LFP with the LFP SCC first while having the Inverter use the GC2 batteries .. when the LFP got to 100% we would then switch it vice versa and have the GC2 charge via its on SCC and use the LFP bank to operate the inverter ...

And we found doing it that way was significantly better than stringing it all together....