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Main Forum => General Discussion => Topic started by: rvrunner on December 31, 2020, 09:09:50 am

Title: AGM/SLA Batteries
Post by: rvrunner on December 31, 2020, 09:09:50 am
I've replaced my flooded lead acid batteries with SLA (Sealed Lead Acid Batteries). As I understand, SLA batteries and AGM batteries have pretty much the same charge rates. I have the multi stage converter which is SLA/AGM compatible for charging, my solar controller is set for SLA/AGM charging, but my 2017 Ford E350 alternator is charging the batteries at a constant 14.4 volts. Is that a little high? I don't think there's any adjustment on the engine alternator? The factory offers both flooded lead acid and agm batteries but I don't think they make any adjustments for charging the different batteries. The only adjusting I think that can be done is on the back of the solar controller.
Title: Re: AGM/SLA Batteries
Post by: Ron Dittmer on December 31, 2020, 10:50:03 am
That is an interesting observation you have there rvrunner.

For the past 5.5 years, our 2007 PC-2350 has been equipped with a Sealed Lead Acid Battery for the chassis, and two 6V-in-series AGM batteries for the house.  When the main V10 engine is running, the volt meters I have for each reads the same 13.6 volts or so.  I never seen a reading of 14.00 volts or higher under any condition, engine idling or at high rpm on the open road, day or night with the headlights on, it fluctuates almost nil.

Because the reading is the same and barely ever changes by miniscule amounts, that tells me the alternator is charging all batteries at the same time and charging them constantly.  I always thought that was odd, but the charging condition has never been a problem.

For the record, our 2007 PC-2350 has no solar (no solar controller) and has the Tripp-Lite 2000watt whole house inverter/converter that was installed by Phoenix when new, and I did set it for AGM technology when installing the two 6V AGM house batteries 5.5 years ago.  I installed the volt meters at the same time so I have no history of charging behavior prior to my current batteries.

Everything has been working fine all these years so I have not fretted over it.  Still I wonder.
Title: Re: AGM/SLA Batteries
Post by: mikeh on December 31, 2020, 01:22:35 pm

Your observations are all pretty much on track.  As you say, the SLA and AGM batteries should have charge rates that fall closely into the same parameters.  The 14.4 volt charge rate that you see from your Ford alternator is nominal.  The E-350 system charge program is set by Ford and is not adjustable--the output of the alternator is monitored/controlled by the Powertrain Control Module (PCM), which receives an input from the alternator and returns an output to the alternator regulator setting the charge rate based on RPM, ambient temperature, system voltage, etc.  To my knowledge, Ford does not alter the system charge program in the PCM based on whether they install FLA or AGM batteries.  Lastly, most (or all) solar controllers do provide more detailed adjustments for the charge program than any other source.

Since your vehicle alternator is not normally the main charge mechanism for your house batteries (not for hours--turning into days--like your converter or solar system), it is not as critical long-term to battery life and condition.  And since 14.4 volts would be an acceptable range for both bulk and absorption voltage for major AGM batteries (Victron, Trojan, Lifeline), I don't believe you have any concerns with your current operation.

Title: Re: AGM/SLA Batteries
Post by: rvrunner on December 31, 2020, 01:44:44 pm
Thanks for the replies, I think all is well.