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

[T1 Terry]

Originally Posted by noelex 77

Thanks for everyone's replies.

The winch draws about 100A. Normal anchor retrieval is only 5 mins or so with the alternator running (but at low revs) so the AHr draw will only be about 5AHrs out of the battery. Perhaps the greatest limiting factor is the discharge will be close to 1C intermittent for 5mins. In the worst case perhaps a 1.2C continuous for close to 10mins.

(The worse case scenario is the main engine refusing to start, perhaps draining the start battery down to 60% with the attempted starts. Then pulling the anchor out without using the main engine which in a strong wind would be using more power say 10-12AHrs. The draw in this situation would be about 120A and close to continuous for 10mins)
It seems to me perhaps 100AHrs of lithium would manage this. Given the small cost difference I would rather go on the larger if I am getting close to limit.

The company sells Sinoploy, Winston and Calb (GWA?) batteries all for a similar price. Have you any thoughts on the better brand.

Winston or Sinopoly for sure, far better chemistry and better QA, maybe even Sinopoly slightly ahead now with their newer cell case design. As the desired discharge rate is only 1C to 1.5C there is no value in looking to cells designed for high rate discharge. at a 1.5C discharge rate either the Sinopoly or Winston LYP cells will give you the full 100Ah capacity if you absolutely need it.
Here is a test on a 90Ah attery using an inverter and a coffee percolator for the load, 4 x 12.5min loads, one after the other, one 10min anchor pull at 120amp would be well within these batteries capability.

T1 Terry

[Lagoon4us]

3 -230 watt solar panels, a 5volt charger and 4- 400 amp cells with logger ordered from EVPower, no tax! Woohooo! Only gets better....

[mrm]

Originally Posted by T1 Terry

My advice would be, link the house battery to the lithium battery with a relay capable of handling 200 amps for a short time but 100 amps continuous, link this to the cell logger alarm via a small relay circuit that demands very little current, the alarm circuit in the cell logger can't handle high current or back EMF. Have a second switch to the relay so it is only closed (on) when the house battery is charging, this way the cell logger will turn the relay (and therefore the charging) off when a cell reaches 3.6v. the relay that drives the larger 200amp relay will need to ratchet in the open (off) position one the alarm port triggers the relay, but auto reset when the power is turned off and then back on.
Connect all charging methods to the lead acid house batteries.

Can the electrical folk here draw up a simple ratcheting and auto reset mini relay circuit?

T1 Terry

Is this what you have in mind?
For now a block diagram, assuming the HVC output from BMS latches high and requires a manual reset at BMS.

Marius

[T1 Terry]

The Junsi cell loger alarm port switches the red wire either to the battery negative or opens the the bat negative connection, the black wire is connected intenally to battery negative. The alarm port can be configured from N/O (normally open, closes with an alarm signal) or N/C (normally closed, opens with an alarm signal) The down side, is the loger has no on time for the alarm switch, as soon as the voltage drops the alarm is cancelled, so either a ratchet the holds the relay open or a timer circuit to hold he relay open for a predetermined length of time, or a voltage sensing circuit the closes the relay again if the battery voltage drops below a certain value. Probably, for this application, a ratcheting relay with a manual reset would be the best choice, it is not desireable for the lithium battery and lead acid battery to remain connected when not charging as the lithium battery has a higher standing voltage and would drain into the lead acid battery dragging it completely flat.
does that fit in with your circuit Marius? I worked out which bit the mechanical relay is I guessing one bits a transistor just below the relay, but the other 2 bits have me thrown :lol:

T1 Terry

[ebaugh]

Originally Posted by mrm

Is this what you have in mind?
For now a block diagram, assuming the HVC output from BMS latches high and requires a manual reset at BMS.

Marius

Do you have an inverter charger? I think that would keep this concept from working.

[T1 Terry]

Originally Posted by ebaugh

Do you have an inverter charger? I think that would keep this concept from working.

This is for Noelex77 and his anchor winch lithium battery charging, it would be linked to the house batteries, in this case lead acid batteries, so the charger would see them as the load, the lithiums could be switched in or out without effecting any charging source.

If the alternator assists the winch supply via the start batteries, the output from the lithium batteries would need to have a diode inline to stop the start batteries trying to charge the lithium batteries while powering the winch.

T1 Terry

[mrm]

Originally Posted by T1 Terry

The Junsi cell loger alarm port switches the red wire either to the battery negative or opens the the bat negative connection, the black wire is connected intenally to battery negative. The alarm port can be configured from N/O (normally open, closes with an alarm signal) or N/C (normally closed, opens with an alarm signal)

Ah, ok, so the logger alarm port is an open collector type drive.

The down side, is the loger has no on time for the alarm switch, as soon as the voltage drops the alarm is cancelled, so either a ratchet the holds the relay open or a timer circuit to hold he relay open for a predetermined length of time, or a voltage sensing circuit the closes the relay again if the battery voltage drops below a certain value. Probably, for this application, a ratcheting relay with a manual reset would be the best choice,

Understood, this means some logic will need to go to the 'HVC interlock' block.

it is not desireable for the lithium battery and lead acid battery to remain connected when not charging as the lithium battery has a higher standing voltage and would drain into the lead acid battery dragging it completely flat.

And I see a potential problem here.

Scenario:

0. Lead acid voltage detector (the triangular item on the left, next to LA battery) has a hysteresis built in. This is required to prevent contactor being repeatedly bounced ON-OFF when charging current hits LiFePO and causes a voltage drop due to higher load on charging source(s). Let's assume Von = 13.2V and Voff = 12.9V;

1. charging starts, Lead acid goes > 13.2V ==> relay goes ON;

2. charging continues, voltages rise, charging stops before HVC levels, so no HVC condition;

3. since there was no HVC, LA and LiFePO remain connected, through a bidirectional high current capable path;

4. since there is hysteresis (as described in 0.), relay will stay ON till voltage in BOTH batteries drops below 12.9V (or some other hysteresis set-point).

Now, it does not look too good to me, but maybe it is OK?

does that fit in with your circuit Marius? I worked out which bit the mechanical relay is I guessing one bits a transistor just below the relay, but the other 2 bits have me thrown :lol:

I added more descriptions to the diagram: http://infinity.eti.pg.gda.pl/tmp/LA-LiFePOv2.png

[ebaugh]

Originally Posted by T1 Terry

This is for Noelex77 and his anchor winch lithium battery charging, it would be linked to the house batteries, in this case lead acid batteries, so the charger would see them as the load, the lithiums could be switched in or out without effecting any charging source.

If the alternator assists the winch supply via the start batteries, the output from the lithium batteries would need to have a diode inline to stop the start batteries trying to charge the lithium batteries while powering the winch.

T1 Terry

OK...makes more sense now.

I just ran a test on the needed current draw to keep my 2 AGM 6V golf cart batteries paralleled to my lithium bank. At 13.2V, the needed float current is 200mA. That's still a parasitic load on discharge, but a rounding error in my installation. 5 Ah per day.

[Maine Sail]

Lets' talk alternator voltage regulator settings.

I have a Balmar MC-614 and have a fairly solid idea of how I want to program it but would like to hear ideas from others too..

So how would you program the MC-612/614 Balmar regulator for a Winston LiFePO4 bank?

[deckofficer]

Originally Posted by Lagoon4us

3 -230 watt solar panels, a 5volt charger and 4- 400 amp cells with logger ordered from EVPower, no tax! Woohooo! Only gets better....

Welcome to the club. What is the 5 volt charger for, did I miss something?

[deckofficer]

Originally Posted by T1 Terry

Winston or Sinopoly for sure, far better chemistry and better QA, maybe even Sinopoly slightly ahead now with their newer cell case design. As the desired discharge rate is only 1C to 1.5C there is no value in looking to cells designed for high rate discharge. at a 1.5C discharge rate either the Sinopoly or Winston LYP cells will give you the full 100Ah capacity if you absolutely need it.
Here is a test on a 90Ah attery using an inverter and a coffee percolator for the load, 4 x 12.5min loads, one after the other, one 10min anchor pull at 120amp would be well within these batteries capability.

T1 Terry

Best test I've seen Terry. Shows how even a 90 a-hr bank can flex some muscles. Too bad you don't have a 2nd graph showing a lead acid 90 a-hr battery subjected to the same test.

[noelex 77]

Originally Posted by T1 Terry

Here is a test on a 90Ah attery using an inverter and a coffee percolator for the load, 4 x 12.5min loads, one after the other, one 10min anchor pull at 120amp would be well within these batteries capability.

T1 Terry

Thanks, a perfect graph for my application.

[T1 Terry]

Originally Posted by deckofficer

Best test I've seen Terry. Shows how even a 90 a-hr bank can flex some muscles. Too bad you don't have a 2nd graph showing a lead acid 90 a-hr battery subjected to the same test.

This battery is roughly 3 yrs old, it showed no signs of being past it'd use by date till this test.

T1 Terry

[T1 Terry]

This Gel battery is less than 8 mths old but has been in regular service.

T1 Terry

[T1 Terry]

Originally Posted by Maine Sail

Lets' talk alternator voltage regulator settings.

I have a Balmar MC-614 and have a fairly solid idea of how I want to program it but would like to hear ideas from others too..

So how would you program the MC-612/614 Balmar regulator for a Winston LiFePO4 bank?

Is this alternator dedicated to house battery charging? Do you plan to use a Junsi logger to drive a charge disconnect relay if a cell goes over 3.6v?

T1 Terry