I have seen too much confusion concerning battery charge rates. In Jeremy's original post he referred to a C20 charge rate. There's more information needed to understand what he meant. It would be convenient if we would all use the same expression to indicate the maximum charge current.
The expression C/xx can refer to a charge rate or discharge rate. Example: the C/10 charge or discharge rate of a 400AH @ C20 battery would be 40 amperes. Or, you can express the charge rate as a percentage. John was saying to charge Trojan batteries at 10% to 15% of the C20 rating. Another way to express a charge rate is xC. This can be written as 0.10C or 0.15C (for 10 or 15%). I like this method best. Larry Crutcher Starlight Solar Power Systems (928) 342-9103 On Apr 2, 2012, at 12:43 PM, Jason Szumlanski wrote: There are a lot of forums and circles where C/20 refers to the capacity divided by 20, or 5% of the battery capacity. This may be the more informal interpretation of the term, but you will find many examples where people consider C/20 to be 5% of the capacity (wrong or right). For example, look at the most frequently accessed deep cycle charging FAQ on the Internet: http://www.windsun.com/Batteries/Battery_FAQ.htm To be clear perhaps we should just use plain English and say “the recommended charging rate is 10-15% of the capacity of the battery at the 20 hour discharge rate.” Jason Szumlanski Fafco Solar From: [email protected] [mailto:[email protected]] On Behalf Of Allan Sindelar Sent: Monday, April 02, 2012 1:46 PM To: [email protected] Subject: Re: [RE-wrenches] Hot Trojan Batteries Wrenches, I attended John DeBoever's Friday afternoon presentation on battery technology and care at the NABCEP Continuing Education conference this past weekend. It quickly became clear to me that John seriously knows his batteries, at all levels: chemistry, physics, RE use and care, etc. It was an advanced-level presentation, and I learned a lot. The first thing John told us was that English is not his native language; he's a Belgian raised in South Africa (and more that I didn't catch). He was bursting with knowledge and good information, but occasionally we in his class would back him up to better explain a point. In short, I think he will be a real asset to the Wrenches list as a manufacturer's representative. And occasionally there will be something confusing, such as what just happened here. I too wondered about C20 versus C/20. I appreciate that he quickly cleared up the confusion, and look forward to learning quite a bit from his posts about battery issues. Allan Allan Sindelar [email protected] NABCEP Certified Photovoltaic Installer NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Positive Energy, Inc. 3201 Calle Marie Santa Fe, New Mexico 87507 505 424-1112 www.positiveenergysolar.com On 4/2/2012 11:00 AM, John DeBoever wrote: Jason, Wrenches, C/20 means C over 20 hours discharge rate = capacity @ the 20 hours discharge rate. C/20 often is mentioned as C20, so the confusion here. Max recommended is 10& to 15% of C20 of the battery bank. John Trojan Battery Company From: [email protected] [mailto:[email protected]] On Behalf Of Jason Szumlanski Sent: Monday, April 02, 2012 12:53 PM To: RE-wrenches Subject: Re: [RE-wrenches] Hot Trojan Batteries There must be some confusion here about the charging rate. C/20 refers to capacity divided by 20, so in the case of a 325aH battery (capacity @ the 20 hour discharge rate) we’re talking about charging at a 16.25 amp rate. I’m sure John is not referring to a maximum rate of 10-15% of 16.25 amps, but 10-15% of the 325aH capacity. Jason Szumlanski Fafco Solar From: [email protected] [mailto:[email protected]] On Behalf Of John DeBoever Sent: Monday, April 02, 2012 12:14 PM To: [email protected]; RE-wrenches Subject: Re: [RE-wrenches] Hot Trojan Batteries Jeremy, Wrenches, 165°F is definitely too high and you should stop immediately any charge to avoid further major problems. I recommend you contact our Trojan Tech Support for help at http://www.trojanbatteryre.com/Tech_Support/Tech_Support.html?tab=0#TabbedPanels1#top Below are few perspectives to help the diagnostic: o System issues: ü Check Charger setting: the C/20 rate mentioned is definitely too high and will damage the battery. The maximum recommended current rate is 10-15% of C/20 for a deep-cycle flooded lead acid battery. Other C/rates are possible but are application specific and not typical. ü Check Voltage settings: these are provided on Trojan datasheets, see here: http://www.trojanbatteryre.com/Tech_Support/literature.html ü Check Temperature compensation: -0.028VPC for every 10°F above 77°F (add 0.028 VPC for every 10°F below 77°F or subtract 0.020VPC for every 10°F above 77°F. See here: http://www.trojanbatteryre.com/PDF/Signature_Trojan_ProductLineSheet.pdf ü Check Voltage sensor status and connection. Dedicated wiring is recommended ü Check temperature sensor. It shall be well positioned, typically in the middle of the battery bank at the warmest point. ü Check if air circulation between the battery units. ü Check if adequate air ventilation of the battery room. o Battery issues: ü C/20 charging rate is too high (see above) ü How old are the batteries? Ageing batteries will face micro-shorts that will decrease the battery turnaround efficiency over time that translates in higher temperature generation. Typically the battery temperature range is about 20oF above ambient temperature, and typical min and max limit are -4°F to 113°F. See here: http://www.trojanbatteryre.com/PDF/Signature_Trojan_ProductLineSheet.pdf 165°F is way too high and will damage the units ü Maybe you are facing one or more shorted units: check the voltage and it will quickly indicate if a unit is shorted. Shorted units will generate heat and will jeopardize the charging of other units. Remove shorted units and consult tech support your charger supplier if possible to reconfigure of your battery bank with fewer units, configured at a lower battery bank voltage, using same voltage settings recommended by Trojan Battery Company. Typically 1 to 3 units less would be acceptable, depending the charger manufacturer settings. ü Maybe you are facing sulfated batteries, resulting from low charging, thus resulting in lower overall turnaround efficiency. This will heat some healthier units of the battery bank, accelerating corrosion damages. The max temperature acceptable being 113°F, please consult Trojan Tech Support: http://www.trojanbatteryre.com/Tech_Support/Tech_Support.html?tab=0#TabbedPanels1#top ü Please deal directly off-Wrenches list, with Trojan Tech Support for better fine tune resolution:http://www.trojanbatteryre.com/Tech_Support/Tech_Support.html?tab=0#TabbedPanels1#top I hope this help, John John F. DeBoever Global Technical Director – Renewable Energy Trojan Battery Company 12380 Clark Street Santa Fe Springs, CA 90670 Tel: +1-562-236-3000 Ext. 3139 Cell: +1-845-514-7600 – NY office time zone: USA EST (GMT-5) Skype: john.f.deboever Fax: +1-562-236-3239 [email protected] www.trojanbattery.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Sunday, April 01, 2012 7:20 PM To: [email protected] Subject: [RE-wrenches] Hot Trojan Batteries Wrenches, Can anyone explain why an L16 bank would be at 165F at rest. Over a C20 charge rate, but I have a feeling there might be an internal short Jeremy All Solar Sent via BlackBerry. Sorry for typos and shorthand! _______________________________________________
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