LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[witzgall]

If I can get them all into the original battery boxes, then the distance might be < 2 feet between the two sets of 3,2v banks.

Chris

Originally Posted by T1 Terry

Hi Chris,

If the distance between the two 6v battery banks required a cable roughly 15ft long it would need to be 000AWG or bigger to carry 200amps and there would be losses, if the two banks were each 12v even though 2 cables would now be required using the same 200amp figure the losses would be negligible.


T1 Terry

[electric1]

Originally Posted by witzgall

If I can get them all into the original battery boxes, then the distance might be < 2 feet between the two sets of 3,2v banks.

Chris

Don't worry about the distance, just use appropriate cable size and even oversize it if you can. Any welding shop can supply 1/0 or 2/0 thin stranded cable with lugs. Voltage drop on a few feet of such cable is negligible. In EVs people split battery banks between front and rear all the time, there is no problem at all.

DO NOT parallel strings of series connected cells. Parallel cells to get desired AH capacity, then string those paralleled groups in a single 4 unit series string for 12V nominal bank. Paralleling strings is asking for trouble in the long run. There is no need for multiple banks either, its a waste of cells/weight/money. Single bank gives you best return on investment.

[T1 Terry]

Originally Posted by witzgall

If I can get them all into the original battery boxes, then the distance might be < 2 feet between the two sets of 3,2v banks.

Chris

Misunderstood what you posted, I thought you were saying the battery boxes were in each side of the boat, not that they were side by side.
I would recommend against using solid bar to link the cells but rather braided link like the ones from EV works or the multiple layer copper straps that Trev from Basically Natural sells. I'm sure there are other sellers with similar style cell links. The cable to link the two battery boxes can either be made up from welding cable like Electric1 suggests or from the cable the car audio people use, this was my choice because the cable conductor is super fine strands but the outer case is a tough hard wearing material. The welding cable is often rubber coated to give it the flexibility but it's not hard wearing and damages easily.
Don't forget to sand the oxide coating off the cell terminals and link straps and paint them with "Alminox" or one of the other anti corrosion pastes recommended for aluminium to copper electrical connections. A simple but time consuming job but will save a lot of future headaches.

T1 Terry

[romanystar]

I'm new here, as a member, but have read most all the threads on this subject. I've seen mention in other places that the ability of these batteries to accept a high charge rate can lead to melting down an alternator that does not have temperature protection in the controller.

I am close to spending the money to change out my tired T145's to 8 CALB 180's. I'm trying to determine which other pieces of the puzzle will need to be upgraded. I already have a programmable shore power source, and an adjustable MPPT solar controller.

The Ample Power alternator controller is nearly 20 years old, but does a fine job of 3 step regulation. Should I be replacing it to get something that will monitor battery temperature? Any suggested products?

Paul

OBTW: Welding cable is not usually tinned and is not a great idea in the marine environment.

[romanystar]

Originally Posted by romanystar

Should I be replacing it to get something that will monitor battery temperature? Any suggested products?

Whoops, meant to ask if there is a suggestion for an alternator controller that monitors alternator temp.

I am aware of the Balmar, but don't like push on spade connectors on the boat.

[T1 Terry]

As long as the voltage difference isn't too extreme cable conductor diameter will control current flow. A balanced 4 cell Li battery will be fully charged at 13.8v (3.45v per cell) so this is the finishing voltage. The cells can handle a higher voltage but there is some evidence that this reduces their cycle life, Jay Whitacre from the Carnegie University briefly touched on this in his LiFeP04 over view.
An alternator charge voltage of 14.4v would equal 3.6v per cell in a well balanced battery, within the capacity these cells can handle, so if 14.4v or lower was set as the alternator control voltage and this was sensed at the alternator end of the cable then basic cable voltage drop tables can be used to determine the most suitable cable conductor diam determined by length and the max amps you want the alternator to put out.
If you use something like this calculator chart (halfway down the page) add in the cable length, say 12ft, 2/3rds the alternator output, say 80 amps, calculate and look down the chart, 0.6 voltage drop would create 14.4v at the alternator but still provide 13.8v at the battery end and this lines up with 8awg cable. Keep in mind DC is a continuous loop circuit so if both cables are the same conductor diameter then the length both ways needs to be added together. If you charge to your start batteries at 14.4v and connect the house batteries via a suitable switch or solenoid you won't risk disconnecting a load from the alternator at any time so diode damage can be avoided.
Hope this helped and didn't just add confusion.

T1 Terry

[witzgall]

I would be much more concerned about monitoring alternator temperature than battery temp. The internal resistance of LIFEPO4 is low, so in my mind this means that the battery temp will rise much less in them when being charged.

However, an alternator that is being asked to pump out max amps for potentially hours at a time may have a short lifespan, if the regulator does not have a way to monitor this and dial back when needed. This is why an external regulator and temp sensor is often recommended. I asked the Balmar folks if their alternator and regulator (612?) would work with LIFEPO4. They were not very interested in saying anything about "fancy batteries" as the guy put it, but he did recommend using an alternator temp sensor.

Chris

Originally Posted by romanystar

I'm new here, as a member, but have read most all the threads on this subject. I've seen mention in other places that the ability of these batteries to accept a high charge rate can lead to melting down an alternator that does not have temperature protection in the controller.

I am close to spending the money to change out my tired T145's to 8 CALB 180's. I'm trying to determine which other pieces of the puzzle will need to be upgraded. I already have a programmable shore power source, and an adjustable MPPT solar controller.

The Ample Power alternator controller is nearly 20 years old, but does a fine job of 3 step regulation. Should I be replacing it to get something that will monitor battery temperature? Any suggested products?

Paul

OBTW: Welding cable is not usually tinned and is not a great idea in the marine environment.

[OceanPlanet]

Originally Posted by romanystar

I'm new here, as a member, but have read most all the threads on this subject. I've seen mention in other places that the ability of these batteries to accept a high charge rate can lead to melting down an alternator that does not have temperature protection in the controller.

I am close to spending the money to change out my tired T145's to 8 CALB 180's. I'm trying to determine which other pieces of the puzzle will need to be upgraded. I already have a programmable shore power source, and an adjustable MPPT solar controller.

The Ample Power alternator controller is nearly 20 years old, but does a fine job of 3 step regulation. Should I be replacing it to get something that will monitor battery temperature? Any suggested products?

Paul

OBTW: Welding cable is not usually tinned and is not a great idea in the marine environment.

I'm a long-time user of Ample Power alts & alt regs, but have had bad luck trying to use their alt regs for lithium. Tried once again on a recent job where there were two SAR-V3's for two big new alts (one American Power Systems 42i-250-14V alt on each engine). They kept having problems...won't go into details here but switched to Genasun lithium-specific alt regs and problems were solved.

The Genasun alt regs and APS alts seem to be a good combo for lithium. Also recently set up dual 42i-160-28V alts & regs to charge a 920Ah x 24V lithium system on the new Telefonica Volvo 70. Combined, the two alts put out well over 400A x 27V when cold and can charge indefinitely at 300+A x 27V. Takes a lot of engine power though. The Volvo D1-30 driving them has to work pretty hard.

[CharlieJ]

I have installed Balmar alternators and regulators on TPPL AGM and LFP banks. Both of these battery chemistries are very, very hard on alternators w/LFPs being the most demanding.

In all cases, I have taken two actions to treat the alternators well:
1. Spec and install the largest case alternator possible and then use the alt regulator to regulate the alt output to about 80% of the its max rated output.
2. Install the alternator temperature monitor to cutback field current, and thus alt output, if the alt temperature exceeds a preset limit (about 220F).

Charlie

[OceanPlanet]

Balmar alts are notorious for overheating. On the plus side they have the temp sense/cutoff in their alt regs to compensate for this...;-)

For TPPL or lithium I like to know the alts can run long and hard without overheating.

[downunder]

Originally Posted by OceanPlanet

Balmar alts are notorious for overheating. On the plus side they have the temp sense/cutoff in their alt regs to compensate for this...;-)

For TPPL or lithium I like to know the alts can run long and hard without overheating.

I noted an article of Nigle Calder's where he had to modify his brothers Balmer to stop it overheating.

Seems a good reason to stay from Balmar.

[Overlord]

I have just bought twelve 200ah lithium ion cells from witzgall and a BMS from cleanpower auto.I have just removed my three 4D lifelines and will start the installation soon

[senormechanico]

I purchased four "tall cells" from Chris as well.
Will install a BMS as well.
Can't wait!

[bill good]

The point is normal belt type of car alternators are not designed for continuous charging but to use them on LIFEPO4 will need to (a) d-rate the alternator (b) use different regulators with constant current / constant voltage design to the requirements of LIFEPO4 batteries. Flywheel alternators will takeover this job in the future. It is the same as an electric motor has a continuous rating like industrial motors but will have a 5 min rating up to 3 times that figure. Heat removal is the limit in design. Automotive & the like normally recharge the starting battery in minutes then their job is to run all the electrical needs of the motor while the battery just floats. It maybe hard work for the engine driven alternator to ever get pass the constant current phase of the curve as required for LIFEPO4.
Regards Bill

[T1 Terry]

Li batteries are energy hungry, they have very little internal resistance so current wil flow into them very quickly. Some form of current limiting would be required if a low otput alternator was used. Possibly even charging via the start batteries instead of direct from the alternator and limiting the voltage to 13.8v would enough. Alternators will run for a long time without overheating at 50% to 60% of the their rated output.
Li batteries wil not slow their acceptance rate like lead acid batteries so another possible method is using a DC to DC charger with a capacity low enough to protect the alternator from overheating.

T1 Terry