Standard charging voltage compatible with AntiGravity battery while installed in NSX?

[Wild Turkey]

OK, looking for folks already using an AntiGravity battery, who may or may not have checked their charging system.

I received my ATX-30RS battery and optimate LFP charger as recommended by AntiGravity. Before I charged or installed the battery, I read the instructions and safety precautions. It states that the maximum charging voltage is 14.4 V on p 1 and and it says to "Test for properly operating charging system in your vehicle by a professional. Vehicles should never charge above 14.4 V." on p 3. I started my NSX with an old battery (reading 12.5 V) and then checked my voltage. My volt meter reads 14.8 V (presumably charging) at the battery with the engine idling. Do I have a defective regulator or alternator and will this toast my AntiGravity battery?

Note: I was asking about voltage on my battery last summer when my gauge seemed a bit high, but concluded that the gauge was just reading a little high. Back then I was measuring 14.6 V at the battery and the service manual says up to 15 V is within spec. It's been working fine with my regular lead acid battery:

How much voltage is too much?

Search on alternator and regulator turned up empty, with most complaints of low voltage. My car starts and drives fine, so I'm not sure there's a problem. All I could find was: https://www.nsxprime.com/threads/do-i-need-a-new-alternator.216688/#post-2040687 Driving around & noticed that my volt...

www.nsxprime.com

I'm planning to call AntiGravity on Monday, but how do I reconcile the service manual being OK up to 15 V and AntiGravity's spec to not exceed 14.4 V?

Thoughts?

 

[Old Guy]

I haven't checked the voltage at the battery terminals (too much hassle); but, last year or the year before I did a quick check on the jump start terminal with the engine running. I can't remember the exact number; but, it was definitely in the very high 14s. That works out for me because I use an AGM battery which generally benefit from a charging voltage that is on the high side.

As to reconciling the service manual being OK with voltages up to 15 volts, I don't think there is any reconciling. It is what it is and on the surface is non adjustable. The alternator voltage regulator does get an input from the ECU which I believe is an AC on signal. I don't know whether this is a binary signal or a variable signal. If it is a variable signal you might be able to fiddle the signal to try and keep your alternator voltage on the low side. However, you are kind of entering into uncharted waters.

I would be inclined to go back to Antigravity and ask them how hard is the 14.4 volt limit and is that a maximum with the recommended voltage being less?

 

[Wild Turkey]

That's what I was thinking as well. I am definitely not going to try and modify the NSX electronics and run at a lower voltage to use a LiFePo4 battery, even to save 20-30 lbs. If I had a faulty regulator, I'd change it, but otherwise, I'll just ask AntiGravity whether I should keep the battery or not. (Warranty...)

The reason for my perplexion is that there seem to be a bunch of Primers running these batteries, so if the standard charging voltage toasts them, I would have expected to see threads on short life expectancy.

I just checked the voltage on a 1995, 14.6 V at the battery when idling. Hmmm

 

[D Baggins]

You’ll probably be fine, we’ve run these batteries on a few daily driven cars at my job and haven’t had any issues as far as overcharging and toasting them goes. The one in my car has even gone dead from leaving it sitting without a trickle charger and hasn’t had any issues after I recharged it. My car is reading 14.4 at idle but I really doubt .2-.4v gonna roast the battery and not be something the integrated bms can’t handle. Doesn’t hurt to call and see what they say though.

 

[Wild Turkey]

I spoke to Chad in technical support at AntiGravity batteries. He told me that the NSX charging at 14.6-14.8 V will not be a problem. The BMS can go up to 15 V, even slightly over 15 V for short periods of time, and the BMS will handle it fine. Apparently they are just concerned about old regulators that can go over 15 V. It remains perplexing that they affix a warning sticker, and the owner's manual also says this.

So we'll give this puppy a go.

 

[D Baggins]

I think they used to have a bunch of problems when guys would buy their motorcycle batteries and throw them on 30+ year old bikes and that’s why they started putting the warning on everything now. The antigravity battery on my R1 actually survived my rotor exploding and before it died the bike was charging it to who knows what even voltage. Even after all that I’ve had no issues with that one and it’s been years since that happened.

 

[WMDNSX]

You’ll probably be fine, we’ve run these batteries on a few daily driven cars at my job and haven’t had any issues as far as overcharging and toasting them goes. The one in my car has even gone dead from leaving it sitting without a trickle charger and hasn’t had any issues after I recharged it. My car is reading 14.4 at idle but I really doubt .2-.4v gonna roast the battery and not be something the integrated bms can’t handle. Doesn’t hurt to call and see what they say though.
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What terminals are you using?

 

[D Baggins]

What terminals are you using?

JL audio XD-BTS and a 1/0 female to 4AWG adapter for the tidy wire connections. If you uncrimp the stock positive terminal both the power wires going to the back and to the front fuse box fit