Lithium Batteries

[yodagwb]

Thinking about switching to lithium batteries given their price reduction vs the price increase of the T-105's. My question involves the alternator. Is the standard alternator set up properly protected it from over voltage/overheating and damaging itself given lithium lower resistance or is it necessary to add a regulator, disconnect or DC to DC charging? Thoughts?

[R.B.]

Most alternators are not able to charge Lithium batteries. Normally you use a DC to DC converter. Here is a demonstration of what could happen:
https://www.youtube.com/watch?v=jgoIocPgOug

[D&M]

I went down this route about six months ago. I removed my 2x100ah AGM house batteries and replaced them with 2 x 200ah Victron superpack lifepo4s. I did not even attempt to use my OEM 55amp engine alternator to charge the batteries. I connected it directly to the starter battery and installed a Victron DC-DC charger, which by the way does not have much to do as I also have 400w of solar going through a Victron MPPT. I do keep my boat on a marina but I have never used the shore power charger (again Victron 1600w inverter/charger). The combination of solar and the DC to DC give me all the power I need. That said I live at 16deg south so lots of sun and no winter.
I sail regularly and are usually on the hook one or two days a week. Lithium - way to go, but don't try to do it on the cheap, you will sleep much better.

In short, no do not use the OEM alternator, do not modify it, save the money and complexity and drop in a DC to DC charger.
Cheers,

DL

[nybor]

Hi David. Since I too am a "David" I completely trust your info on changing over to LB. I have a wind generator (300 W), a 325 W solar panel and 3 - 200 Ah lifeline lead acid batteries. They are so heavy, they even roll my 350 Catalina to port!

So, it seems you are convinced that LB are the way to go and I am seriously considering it, but scared of the alternator response to charging them. I usually only use the solar/wind for charging, but in Florida, the heat and humidity is such that I plug into shore power to run an a/c - dehumidifier.

So, can I get by with the OEM alternator supplemented by the addition of a DC-DC charger? Would it simply be placed inline between the alternator output and batteries? Is the DC-DC used to limit the input to the LB bank?

Thanks again for you info. By the way, I have a BlueSky MPPT 3000i controller.

regards, Dave
ps. I was rooting for Australia. Now, all I care about is Argentina beating France!

[Olivia Mae]

I'm still a tried and true flooded lead acid guy, but thought I'd post the following link to a drop-in LiFePO4 article written by one of the experts in the marine electrical business. All you ever wanted to know and more . Hope it's some use to those considering the conversion.

https://marinehowto.com/drop-in-lifepo4 ... -consumer/

[D&M]

In answer to the questions of can you get by with the standard alt. Yes you can but only with the dc to dc charger. My dc to dc cannot be limited so it will pass through up to it’s max, which is 30 amps. I have hardwired the alt to only the starter battery. Bypassing the combined switch so there is no option of connecting the lithiums to the alt. I still have a cable going from the engine on off switch to the 1-2-all switch but per the marina how to article this is marked as house and emergency. IE this would connect the engine start battery to the DC panel for emergencies only. Glad to say I have never used it.
Seems Argentina came up with the goods - just.

[yodagwb]

MADE THE SWITCH. Installed a single 200ah lithium house with a sealed flood starter bat connected via a DC to DC charger to the lithium. The DC-DC is a 40amp but can be set (which it is) to send 20 amp to the lithium. I can flip a switch and send 40 amp to the lithium if needed but I figured why stress the alt if not needed. Definitely doesn't seem needed. In the morning the house battery is down to about 67% and if motoring, completely filled in about 3-3.5 hours. If just sitting waiting for the sun to come up, the 490-watt panels have it fully charged by about 1:00pm. I did install a shunt to monitor the battery status. So far, I am ecstatic with the switch. Truns out the refrigerator is working better than ever, it is working the way it is supposed to. It now cycles on and off, no frost build up, freezer 25, refer 36 degrees. That only took 20 years. Who knew the compressor would love 13.4 volts as opposed to 12.6v, but it makes a world of difference.

Used a Renogy 40amp DC-DC($136), a Renogy 40 MTTP controler($177), 2 ANL fuses($23), Renogy 500A shunt(67), 200 AH Power Queen lithium battery4(642).

[D&M]

Thanks. It is important to note that the only way to measure capacity of lifepo4 batteries is to use a shunt/ammeter. Great news about the fridge and an important point to make. Li batteries have 13 v on tap continuously until they are flat. Which is why you need the shunt. Volts tell you nothing with Li but once you master this, feel free to take your batteries down to 20% state of charge if necessary. BTW Victron do not count a Li battery cycle unless the charge goes below 60% before recharging. In two years I figure I have about ten cycles on my batteries.
(Caveat I have 400ah of Victron super pack)