med gel vs hi agm

[yeshelp]

Hi i went with agm MK 79ah 8a24 ,it is better than regular agm i hope. was the best i could do.

I read somewhere that when receiving a pair of new batteries we need to connect them with one each other and not machine . maybe to ballance or something like that .

Is that true? if yes do i connect the pos with the positive with cable A . and the neg with neg with cable B?
or positive to neg (seems dangerous)

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with what type of cables?

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Do i need to do that before the first charge ( within the wheelchair) or after the first charge??

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anything esle i should do?
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thanks for your expertise.

[Burgerman]

Any cable size. Connect neg to neg. Pos to pos. Wait 24 hours. Then fit in chair and charge for at least 16 hours.

it is better than regular agm i hope.

nope.

[Swan T.W.]

Hi i went with agm MK 79ah 8a24 ,it is better than regular agm i hope. was the best i could do.

I read somewhere that when receiving a pair of new batteries we need to connect them with one each other and not machine . maybe to ballance or something like that .

Is that true? if yes do i connect the pos with the positive with cable A . and the neg with neg with cable B?
or positive to neg (seems dangerous)

--

with what type of cables?

--
Do i need to do that before the first charge ( within the wheelchair) or after the first charge??

--

anything esle i should do?
--

thanks for your expertise.

Battery boost cables work.

[yeshelp]

ok cool thanks

[yeshelp]

As long as you take it off charge in 24 hours it will HELP as it charges the battery when the 14.4v bit stops too soon. Just make sure you ignore the green, charge for around 16 to 20 hours at least once a week.

HI so i got them plugged and what a releif for now , no more emergency charging.

my joystick gradation does not seem very accurate but having done a day with a lot of distance, the battery still has at least 75 % in it.

i estimate that i will only use 10 to 25 pourcent per day so end of day 90% and 75 % left.

now i also have a functionning timer countdown that does 24 h so here are my questions just not to overcharge them without necessity.

you wrote to charge once per week durint 16 20 hours. is that true even if i start the charge and there is already like 80 pourcent already in there?

Also for the others day of the week considering at the end of the day it is still charged to 90% to 75 % how many hours do you suggest i plug it in (i can use the timer)

tx
i know it is maybe hard to say but something tells me that if i plug it for 24 hours when the pourcentage at the end of the day is 90% it will not be good.

[daveonwheels]

charge EVERY day!!!

[Burgerman]

my joystick gradation does not seem very accurate but having done a day with a lot of distance, the battery still has at least 75 % in it.

You cannot know that. A battery meter like the one on your chair works on battery voltage. And battery voltage DOES NOT tell you the state of charge. Even if calibrated correctly. Its voltage depends on many things. That are usage and history and peukert related. A battery meter is at best a completely innacurate and non repeatable guide. You can basically ignore anything it tells you. It can tell you its full after a 10 minute charge. It can tell you its empty after going up a steep hill whan its not. Its a bullshit device meant mostly as a "comfort" to chair users.

i estimate that i will only use 10 to 25 pourcent per day so end of day 90% and 75 % left.

Its literally useless to try to estimate anything at all on a battery gauge. The chair needs a FULL 16 to 20 hour charge even if you only use 5%.

now i also have a functionning timer countdown that does 24 h so here are my questions just not to overcharge them without necessity.

Throw it away. You WANT the battery on charge as long as you possible can and at least 16 hours if possible daily. You CANNOT overcharge even if its on charge (float) for a week. And this is beneficial.

you wrote to charge once per week durint 16 20 hours. is that true even if i start the charge and there is already like 80 percent already in there?

Its absolutely true, even if its at 99% full.

Also for the others day of the week considering at the end of the day it is still charged to 90% to 75 % how many hours do you suggest i plug it in (i can use the timer)

As long as you possible can. A full day would be great. But if you need to get up and use the chair do so.

tx
i know it is maybe hard to say but something tells me that if i plug it for 24 hours when the pourcentage at the end of the day is 90% it will not be good.

Just the opposite. Thats absolutely the best thing possible!

[yeshelp]

And its too low current means it will take forever at CC and then stop CV too soon. Its too high float partly makes up for stopping too soon. But if left connected for a day or so also causes overcharge to both types of battery... Its charge voltage is correct for AGM, but it ends early and then applies a too high float in an attempt to catch up... At least thats what the label tells me! So bestsuited for AGM allow at least 16 hours to charge. Preferably 20.

hi
ok i took good note that the joystick indicator is not reliable.

i reread this quote . i have agm mk and the charger standing upward . what is the consequence of too high float. i imagine that overcharging has bad consequences. At the same time you advice to plug for 16 20 hours daily if possible even if i use only 5 pourcent. I dont quite understand why. it would lead to overcharging wouldnt it ? Could you explain me thanks

[Burgerman]

i reread this quote . i have agm mk and the charger standing upward . what is the consequence of too high float.

A correctly charged battery only needs 2 stages, and no float. But 99% of chargers stop stage 2 (CV at 14.1 for gel, 14.5 or 6 for AGM) WAY too soon. Why? Because they are a one size fits all, dont have the accuracy or ability to measure low termination currents etc and because they are cheap and cheerful...

A GOOD charger like the PL8 can be manually configured to end charge at around 1000th of the capacity in Ah, so a 70Ah battery would end charge when the charge current, naturally fell to 70A. or 8 to 10 hours at CV. But cheap mobility chargers dont. They stop way too soon. And rely on a low voltage float to complete the charge.

So then they REDUCE voltage to a float level. What is float level? Its the natural voltage of a 101% charged battery. Typically 13.4V per battery. At this voltage the battery voltage and the chargers float voltage match at 100% charged. At this point no current can flow as both battery and charger are now at the same voltage. And so at the CORRECT votage there is no charging going on once the battery reached FULL. But at this lower float voltage this takes a very very long time. And its obviously safe to leave it connected indefinitely.

In order to speed this up a higher voltage like 13.6V is used. This is also safe for up to a week or two. Because while its faster to top up that last 1 or 2 percent, its still not enough that any significant current still flows once full.

Some chargers have float at 13.8V. This is only safe for around 1 to 2 days. But completes the charge faster.

i imagine that overcharging has bad consequences. At the same time you advice to plug for 16 20 hours daily if possible even if i use only 5 pourcent. I dont quite understand why. it would lead to overcharging wouldnt it ? Could you explain me thanks

The only way to OVERCHARGE a lead battery is to leave it on charge for more than 12 hours. Charge means CV voltage. So 14.1 (28.2V) FOR GEL and 14.6V for AGM.

You CANNOT overcharge a lead battery on its correct float voltage.
13.3 to 13.4V is not only safe but the BEST way to store batteries long periods.
13.5 to 13.6 is what most chargers use for float. Because it tops off the battery and is safe at this voltage indefinitely. Although slightly less is better for long term storage.
13.7 to 13.8 is best to hurry up the charger to 100% but not good for longer than a few days.

[Burgerman]

See here. Dotted line is charge AMPS.
Solid line is the voltage the charger presents to the battery.

Note that there is a falling current at constant voltage. Note that this CV (constant voltage) ends, and your charger gives you a green light. But that the current is still actually charging the battery (but still dropping) on the float stage. This is happening AFTER your green ready light. It continues to drop, over around 16 hours. Untill theres almost zero current flowing at float voltage.

This is GOOD!!! It prevents your battery sulfating, and dying. You MUST charge daily, and often. They love being 101% full. And you cannot overcharge them with a decent charger. Even if left on float for weeks or years.

[yeshelp]

Thanks Burger Man,
i understand better now.
the charger saying ) Model4C24080A Output Current (DC)8A±5% Charging Voltage (DC)28.8V±0.2V Floating Voltage (DC)27.6V±0.2V Input Current (AC)3.8A max.
What i understand is that an important information that they dont tell is at which amp does the charger go from CV to Float.

So my guide lines will simply be to plug it as soon as I arrive home and just leave it plugged until i leave. Since somedays per month i can leave it for 24 hours or more that should do it for complete charging from times to times .
Thanks a lot for your patience and helpingwillingness

[Burgerman]

What i understand is that an important information that they dont tell is at which amp does the charger go from CV to Float.

Thats always the problem they never do.

But if it does so at approx 4 hours its way too soon and will need 24 hours extra to fully charge and saturate the battery. If it does so after 6 hours i will take a further 16 hours...

If it sits at CV (not the first stage) for 8 hours then its charged and needs no float. As thats around 500th to 1000th C on a healthy battery.

14.4V (28.8) is ok for AGM. Not gel.
27.6 float is going to complete the charge fast as thats quite high. But do not leave this on charge at that float voltage for more than a day or two absolute maximum.