Technical Manual

Document No. 6-0101 Rev. F Page 31 of 40
11. Do all the batteries in a series string have to be the same model/size?
Yes. Do not mix different models/sizes of batteries in the same string.
12. Are there any issues with having parallel strings of different battery models/sizes, as long as each
string has the same model/size battery in series?
No, since the strings are in parallel they will operate at the same voltage level and will self-regulate. Refer
to Section 5.2 for proper installation procedures for parallel strings. Make sure the batteries are all at
100% state of charge before connections are made.
13. Are there any issues with adding a new battery string in parallel with an old string?
No, since the strings are in parallel they will operate at the same voltage level and will self-regulate. Refer
to Section 5.2 for proper installation procedures for parallel strings. Make sure the batteries are all at
100% state of charge before connections are made.
14. Is it better to use 2V, 6V or 12V batteries as building blocks to make a 24V or 48V battery bank?
As long as the total voltage and capacity of the bank is equivalent, it doesn’t make a lot of difference
which voltage is selected for the building block. To minimize the number of parallel connections in higher
capacity banks, it is sometimes preferable to use 2V or 6V batteries instead of 12V batteries. However,
having just one string of 2V or 6V batteries may not be the best choice because a single point failure in
that string would take down the entire bank.
15. How do I know when it is time to replace my battery?
Replace the battery when it no longer is capable of supporting the discharge load for the minimum
required run time. See Section 5.7 and/or Section 5.9 for capacity testing procedure. Note: short duration
load tests and impedance/conductance measurements are not reliable to determine the actual capacity of
a battery.
16. Can I replace one or several bad batteries in a series string without affecting the other batteries in that
string?
Unless the string is fairly new (less than 12 months year old), replacing only the bad one(s) will cause the
other batteries to be under-charged and/or over-discharged, which will negatively affect their performance
and remaining life. Therefore, it is best to replace the entire string. However, if it is decided to replace only
one or some of the batteries, make sure all the batteries are at 100% state of charge before connections
are made.